The Witcher 3 (mainly the DLCs), the story was so good, like it's the only game I can remember where I was waiting to play it every weekend just for the story.
Ocarina of Time - the music is so amazing, I can still remember all of it.
Runescape Classic (like 2002) for making me impervious to scams - you get scammed by some players once and that sticks with you.
Man, I feel so stupid. When I played the Witcher 3 and finished the main storyline alongside all the non-DLC side quests, I was so impressed that I went "Man, this was amazing. This is as good as it gets. This was the best video game I have ever experienced by far! I want it to stay that way. I'm not gonna drag it on and leave it here." and didn't play the DLCs! And then went ahead and sold my PS4!
Ever since all I've been hearing from people who also played the game is how awesome the DLCs are. Everyone says they're even better than the main storyline. I feel like a massive idiot lol.