I wonder how long it will take for this thread to dissolve into a pissing contest about great games that happen to also look good :p
Anyway, i honestly can't think of any games that were well received (by both critics and players) based purely on their looks. Visuals can add a lot to an already great game, but they do little to help a shitty one seem better.
By the way d21, you might want to edit the OT or title :p They're asking different questions (though they are in theme with each other).
Edit: if we widen the search from visuals to tech in general, i'd say GTA4 seems a lot worse than it once did. It received a looot of praise for how "alive" its world felt (thanks to the PS3/360's new hardware), which masked a lot of its flaws. Now that we have many other open world games with considerably more interesting worlds, those flaws are a lot more apparent.