I'll second the third for Pokemon, I can always pick up Pokemon Red and just blaze through the entire game with just my Charizard lol.

Aside from Pokemon, I'm gonna throw out Growlanser 2: The Sense of Justice, just because I love damn near all the characters and the fact that your choices actually affects the game, storyline, and girl you end up with in the end is just legendary, I keep playing it over and over and over again.

Another one would be Breath of Fire Dragon Quarter for the PS2, probably one of the best RPGs I ever played, although recently I haven't played it much (kinda going thru the other 1000s rpgs I never played), but I'm thinking as soon as I beat the games I want to be, I'll go back to my roots until something new comes out.

I'll also throw out Shadow of the Colossus, something is just epic about running around jumping on giants and slaying them... mmmm not to mention the music makes slaughtering them all the more worthy.