Grey's Anatomy has been on for such a long time, it's hard to believe that there was a time when it wasn't part of our daily lives. It's been 15 years of doctors Meredith Grey, Alex Karev, Richard Webber, Cristina Yang, and everyone else, and we wouldn't have it any other way.

Any fan of the show will tell you that, yes, it's started to decline in quality. That's not to say it's not still good, but it's just not the level it used to be at. Most of us are still watching because we've been with the show so long, but nothing will beat the early seasons of the medical drama.

Instead of focusing on the negatives, let's take a look at the best episodes the show has ever seen. Obviously we can't put all of them on here, but these are the episodes we'll never be able to forget, for better or for worse. Keep in mind: these are in no particular order.

1. Into You Like A Train

Episode: Season 2, Episode 6

Why we won't forget it: This was the episode that made us all sob, and I'd argue it was the first time we really understood just how good this show was going to be. Bonnie and Tom, two characters we've never met before this episode, come to the hospital after being impaled on a metal pole in a train crash.

We grew to love these characters in the short time we knew them, and when Bonnie realized she was the one who was going to die, it was absolutely heartbreaking to watch how she handled it. Meredith didn't want to leave Bonnie to die, yelling "What about her? We can't just abandon her?" It gives me goosebumps to think about it. Bonnie was young, she had so much life to live, and she died with grace.

2. Dark Was The Night

Episode: Season 8, episode 9

Why we won't forget it: All Cristina wanted was to learn from Teddy. Teddy was the first teacher to really teach Cristina about cardio, so when Owen convinced Cristina to operate on Teddy's husband without her knowledge, you just knew it was going to end poorly.

While on the table, Cristina can't save Teddy's husband, Henry, and he ends up passing away. When Cristina finds out that it's Henry, you can feel the crushing sadness. I remember yelling at my TV during this episode, but I don't know if I was yelling in anger at Owen or yelling in support of Cristina. Honestly, it was probably both.

3. Didn't We Almost Have It All?

Episode: Season 3, Episode 25

Why we won't forget it: How could I ever forget Meredith having to cut Cristina out of her wedding dress after Preston Burke left her at the alter? I won't forget, I can't forget. This was one of the most pinnacle moments of the series, because even though it was heart-wrenching to watch Cristina lose the love of her life, I truly think it made her a better person.

If Cristina had married Burke, I think she would have lived in his shadow and wouldn't have grown into the strong, incredible surgeon she came to be. What made Cristina so special was that she knew her career was what she wanted, and she didn't let anyone get in the way of that.  

4. Now Or Never

Episode: Season 5, Episode 24

Why we won't forget it: George O'Malley deserved better. He did. I know he died a hero, and I know he was doing the right thing, but poor George deserved to have a wonderful life. At the very least, he deserved to die with his friends and family being able to recognize him.

When George came into the hospital, no one knew it was him, but there was a feeling that John Doe would end up being someone the audience recognized. As George starting writing "007" in Meredith's hand, I'll admit I didn't know what it meant at first. Then it clicked. Then I cried. To me, this was the saddest death on the show, but George deserved more than what Seattle Grace Hospital could give him.

5. Flight

Episode: Season 8, Episode 24

Why we won't forget it: Some will argue that the plane crash episode of Grey's is where it jumped the shark, and I can see where they're coming from. How could a plane crash in the woods and not kill everyone, or at least seriously injure them?

That being said, the episode still crushed all of our emotions. There are many moments to choose from, like Arizona Robbins screaming as her leg is completely destroyed, or Derek having to break his own hand to save himself, but there's no doubt that the worst moment of the entire episode was watching Lexi Grey slowly die while trapped under the plane. Mark Sloan was there to hold her hand and tell her he loved her, but Lexi should have ended up with Mark, and they should have had cute babies, and she should. not. have. died.

6. Song Beneath The Song

Episode: Season 7, Episode 18

Why we won't forget it: Judge me all you want, but I loved the musical episode of the show. Yes, i know it was cheesy, but I love musicals and I love Grey's Anatomy. Not to mention, the episode was extremely emotional.

Callie Torres and Arizona were put through the ringer throughout their relationship, but nothing was more trying than their car accident. Callie, who was pregnant at the time, flew through the windshield and was on death's door. It wasn't until her spirit came into her hospital room that Callie finally woke up, and learned that she had a daughter. Watching Sara Ramirez, who plays Callie, sing "The Story" still gives me goosebumps.

7. Going, Going, Gone

Episode: Season 9, Episode 1

Why we won't forget it: This episode was downright unfair. After the plane crash, we thought Mark was going to be okay...but we were wrong. When Webber explains the "surge" to Mark, where patients who are dying get a last boost of energy before passing away, you knew it wasn't good.

You could make a solid argument that Mark was the character with the most growth on the series, second maybe to Karev. He went from a womanizing serial bachelor to a man in love and a father. He was just starting a new chapter in his life, and even though Lexi was gone, he still had his daughter Sophia. Sadly, the entire episode was basically a eulogy for McSteamy, and we cried through the entire thing.

8. As We Know It

Episode: Season 2, Episode 17

Why we won't forget it: "It's Meredith. The girl with the bomb is Meredith." This is one of the most iconic lines of the series, and it came towards the end of the second season. Even though we knew Meredith wasn't going to die (it's called GREY'S Anatomy, after all) this episode saw our heart rates go through the roof.

The tension the show was able to create in a short amount of time is nothing short of miraculous. Watching the team wheel the hospital bed down the hallway had me on the edge of my seat, especially when they almost hit the stanchion on the floor. Plus, watching the bomb squad guy get blown to bits after you thought everyone would be okay scared the living daylight out of us all.

9. Walk On Water/Drowning On Dry Land

Episode: Season 3, Episode 15 & 16

Why we won't forget it: I hear a lot of people say that this is when they started watching the show, and to those people I say...what took you so long? The ferry crash episodes were some of the most iconic of the series. Again, you knew Meredith couldn't die, but the longer she was unconscious, the more you started to wonder...are they actually going to kill her off?

The thing that struck me the most about these episodes were the relationships between all the characters and how much Meredith meant to them. From attendings, to residents, to all the interns, everyone showed genuine concern for her life. Despite the drama and fights that happened between everyone, when one of their own went down they were there to help.

10. Unbreak My Heart

Episode: Season 12, Episode 11

Why we won't forget it: I am unashamed of my love for "Japril," which is the couple name of Jackson Avery and April Kepner, of course. Their love story started out as a fun fling, but their feelings for each other grew and grew. Tragedy struck when they lost their first child, Samuel, to a genetic disorder, and they were never the same since then.

This episode showed us the love story of Japril through a series of flashbacks starting at the end and taking us back to the beginning. It let us see where everything went wrong, while also reminding us the love that these two had was absolutely real.

11. Losing My Religion

Episode: Season 2, Episode 27

Why we won't forget it: Denny Duquette was flawed, yes, but that's what made him and Izzie Stevens such an intriguing couple. When they first started flirting, I was skeptical, but then things grew into something special and I really was rooting for them.

This episode is the one where Denny died, and we watched Izzie show up to the hospital in her prom dress, only to find out her fiancée had died. Just gut-wrenching. We also had to see Karev pick Izzie up and carry her home, which somehow made things even worse.

12. Deterioration Of The Fight Or Flight Response

Episode: Season 2, Episode 26

Why we won't forget it: Cutting the LVAD wire was a dumb choice, but in the defense of the interns...they had no idea that Burke was going to be shot in the ambulance bay that night. In theory, though it was insane, their plan made sense. But what you have to remember about Seattle Grace Hospital is that nothing can ever go right.

When Izzie is manually pumping to keep Denny alive, you can feel the fear through the screen. Everyone knows they've messed up, everyone knows Denny is dying, and everyone knows nothing will be the same ever again.

13. How To Save A Life

Episode: Season 11, Episode 21

Why we won't forget it: If you ask me, this is where the show jumped the shark. I know why Derek Shepard had to die, because they didn't want his and Meredith's love story to end in divorce, but was this really any better?

We won't ever forget this episode, because it was a pivotal moment in the series that changed its course forever. However, it was far from perfect. That doesn't mean we didn't cry our eyes out, though, when Zola asked Meredith if she was going to be able to fix daddy.  

14. Fear (Of The Unknown)

Episode: Season 10, Episode 24

Why we won't forget it: Cristina Yang was, and remains to this day, one of the best characters to ever appear on Grey's Anatomy. Even though I hated that she had to leave, I felt like she got to do it on her own terms, and as the best version of herself. Plus, she didn't leave via a massive tragedy, so let's call that a win.

Cristina left to better her career, and she made sure to leave Meredith with some of the best advice on the planet. "You are a gifted surgeon with an extraordinary mind. Don't let what he wants eclipse what you need. He is very dream, but he is not the sun. You are." Wise, wise words.

15. The Sound Of Silence

Episode: Season 12, Episode 9

Why we won't forget it: We always knew Meredith and Alex were close, but this was one of the first episodes after Derek's death that we really witnessed the intense friendship they share. After Meredith is attacked by a patient, Alex is by her side every single step of the way. You can see the fear in his eyes when Meredith is hurt, because you know that they're not just friends...they're family.

When Alex brings Meredith's kids in to see her, he says "you've been asking me every day, 'when can we see Mommy?'" which means he's been caring for her kids while she's been in the hospital, or at the very least has been seeing them every day. It shows Alex's growth, and it shows Meredith's resilience.

16. Stairway To Heaven

Episode: Season 5, Episode 13

Why we won't forget it: This episode is the second half of a two-parter, and while most people may not have it on their list, I think it's a very crucial point in the series. A death row inmate is brought to the hospital, and Meredith is doing her best to find the good in him. Derek doesn't agree with it, but when Meredith goes to the prison when the patient is killed, Derek is there waiting for her after it happens.

This is also the episode where Izzie finally accepts that there is something wrong with her, and that seeing Denny isn't just a fun game. Something isn't right, and she needs to find out what is going on. We all knew from the beginning that it wasn't going to be good, but watching Izzie finally come to terms with it somehow made it more real.

17. Sanctuary/Death And All His Friends

Episode: Season 6, Episode 23 & 24

Why we won't forget it: These two episodes are the best in the entire series, and I'll argue that fact until I'm blue in the face. I could watch them one hundred times and still feel the same tension, despair, and sadness I felt the first time around. I don't even know where to begin. When you find out there's a shooter in the hospital, and then see him in the elevator with Cristina, you can't help but hold your breath.

Then, after Derek gets shot and Cristina is operating on him with Jackson, Meredith telling the gunman to shoot her instead of him is an extremely selfless act of love that we'll never forget.

But perhaps the most upsetting moment was after Charles Percy got shot, and Miranda Bailey realized all the elevators were on emergency stop and she wasn't able to get him help. As she sat and cradled Charles in her lap, and he asked if he was dying, the emotion displayed in Bailey's face was nothing short of heartbreaking.

So there you have it. Our list of the most unforgettable Grey's Anatomy episodes.

Which episodes are on your list?