how is it a sleeper title? the Mario franchise is a big one.
i personally didn't care for Mario 64 at all. it really cool being one of the first 3d games i ever played, the controls were awesome, the graphics rocked at the time too. but the gameplay was tedious and the game was easy for me. of course i say this in hindsight, if i was in a room and had to pick several games to play today, i certainly wouldn't pick Mario 64. but at the time i probably would have.