Mystical Ninja starring Goemon: as a kid I liked this game almost as much as I liked Zelda
Gauntlet Legends: awesome multiplayer hack n' slash RPG, still great fun to play
WipeOut 64: probably better than the PSX versions because of superior controls
International Superstar Soccer: way better than FIFA games back then
Doom 64, Duke Nukem 64, Quake II: great renditions of classic shooters
Man, N64 was a beast.