Preach JCC!
My nominees are...
Super Mario RPG (SNES): I couldn't stop playing the damn game...
Legend of Zelda (NES): I really felt like I had accomplished a feat when I beat the game without a player's guide.
Dragon Warrior (NES): This game was fucking awesome. I hope someone can come in here and back me up
Kingdom Hearts (PS2): The ending wasn't the best, and the camera control wasn't up to super awesomeness, but the game was so freaking addicting. Not to mention, I mark for Winnie the Pooh.