MGS4 is less a game and more a cinematic, immersive, interactive experience, full of faults and amazing anyway.
MGS4 is a deeply flawed game. The story-telling often devolves into cliched melodrama, and, occasionally, the dialogue is painfully simplistic. The pacing between cut-scene and gameplay sometimes evokes ennui and boredom. The humorous elements nearly always fail and there are an embarrassing number of "fan service" moments. The convoluted story will almost certainly madden gamers new to the MGS series and will sometimes even cause confusion for MGS veterans. The gameplay is solid, but ultimately linear and a stealth approach is largely unnecessary - it's much easier to simply gun your way through.
And yet... the game's flaws are much like the flaws of a person - they grant depth, creating a multi-dimensional experience which only highlight the game's strengths.
There's an earnestness to the story that pulled me in. There were moments that I forgot that I was playing a game. Yes, the graphics, polish, and interface are that good, even though they are 3 years old. The technical aspects of this game are near perfect.
And yet that is not why I enjoyed the game as much as I did. Beautiful graphics, largely fantastic voice acing, solid gameplay, memorable (if not as memorable as MGS1/2's) boss fights, these are all great. But still they are not why I give a game with so many flaws a 9.5.
Instead... and perhaps few would understand this - few, likely, would even notice it - but I give this game a 9.5 because of a subtle melancholy that's woven deep throughout the game. The MGS series represents the life work (20+) years of its creator, Hideo Kojima, and this game felt like he was saying goodbye to it.
Near the end of the game, the characters speak of an age that has passed. And, I, who fondly remembers his time playing MGS1 and 2, can only agree. As the credits rolled for MGS4, I, too, felt that an age had ended.
(I wrote this review, not to convince you to play MGS4, but rather to educate you how to approach it. I hope, so armed, you know enough to see the game as I saw it - as one storied designer's farewell to his beloved series).