Well that was an easy poll since FFVI is actually my favorite game ever.
None of the other games register on my favorite games list. I haven't played all of them though. And to be fair I've never played all the way through Z:LttP so who knows if I'd consider that one of the greats if I did. Super Metroid is a great game but I think its reputation is overblown a bit - great game but I would never consider it one of the best games ever.
Mega Man X and Pac-man are great (though I prefer Ms Pac-man). Streets of Rage and Fable are good. Haven't played Dark Souls or The Witcher, and could care less about GT games.
So FFVI by MILES!