Well, my favorite game of all time, is MGS4 so far, it has had though competitionwith Bioshock and other games, but is still my top one with all the other MGS games of course, exept MGS2... Anyway, worst part in MGS4 is actually the part where you fight of the geckos from REX, yeah it's a spoiler but if you havent played it yet gtfo. That's the only part of the game that's ever pissed me off.
But MGS4 is like all good games, not perfect, I'd give it a 9.9, but we'll see, the future might bring that perfect game

I only wish the Halo and Mass Effect fanboys could stfu meanwhile... Don't smile GOW3 fans, all big exclusives are overrated! (well... exept Uncharted, it is an awesom game but not the best either o.o)