I see this is kind of an old thread, not sure if the discussion is still going, BUT ANYWAY
I wouldn't say FFVI is the best game ever made. I'm willing to give it best FF but that's tough to do, not because VI was lacking but because a couple of the others were also genuinely very good. Likewise, I miiiiight concede it best RPG, although again that's a very tough call.
But best game ever, no. There are just other games that I think did gameplay, story, characters, etc. better.
THAT SAID, I do think the opera scene is probably the greatest single scene any video game has ever done. Ever. It's just... perfect.