I'm surprised no one has mentioned the Pokemon gameboy games.
1) Pokemon Red/Blue/Yellow... and all the rest too
2) Tales series. Only played Symphonia and some of Vesperia but definitely love it.
3) Chrono Trigger - just started playing this again on my n900 ^_^
Games I know I'll like but haven't played yet: Skies of Arcadia and Lost Odyssey!