could it be the music?
ALl the 'best game of all time' have one thing in common, they all have exceptionally high quality music, usually from such and such composer.
Well no doubt all the best games of all time would have the best parts of everything for its time, there are games that get lost, which are great, and more than worthy of being called 'greatest game of all time' by a bunch of fanboys, but aren't.
I mean, we have Zelda: OOT, FInal Fantasy series, Super mario bro series (yes, kinda different but the music is still a standout :p), erm, more but I can't remember :P
Then we got other great games that never hit big, like secretes of evermore which lacked the epic music...
just an observation...