Kingdom Hearts 1-easily my favorite game. I love most everything about it. Yes, nostalgia plays a factor there as it was my first PS2 game, But i still enjoy playing it years later.
Ratchet and Clank 2/3. Pure destruction. Pure fun. Easily in my top 5 games If you can only count one game there, put my vote for 2
Twewy-great atmosphere, felt like the game was alive
Pokemon Heart Gold- I've been unable to put it down since for 180 hours of gameplay since i got it. So much to do, and its really enjoyable. Feels like an actual pokemon world.
Tough, but going with LoZ Link to the past for the GBA. Great, long, and epic. has had years of enjoyment. Its the oldest game i still play, in fact.
Twilight Princess, Mystery dungeon red, and ffx were strong contenders, But I'm sure of my 5. What made me go with my five was lasting appeal. I want to be able to pick up a game years after getting it, and still enjoy playing it. Twewy is the exception for amazing first impression. And heart gold, like I said I haven't been able to put down for almost 2 months now, and i'm not done with it yet. It has an awesome amount of stuff to do