NES - Dragon Warrior, Final Fantasy, Ultima - Exodus, Crystalis, Xevious (better than the 7800 version, IMHO), Star Voyager (Yes, I know that makes 6)
SNES - Dragon Quest I & 2 (J) (Unless you acquire the Japanese cart and learn your way around the menus you'll probably want to play the translated version on an emulator), Final Fantasy - Mystic Quest (it's an RPG on training wheels but it's still fun)
Sega Genesis - Golden Axe, Streets of Rage, The Fairy Tale Adventure (Fairy is spelled differently than that), Sonic, Lotus II, Columns (Yes, another 6)