If Kojima is going to keep making games like this, he better get better at making movies.
With a variety of ways to dispatch the enemies and a sharp interface to customize your weapons, decimating countless grunts is profoundly enjoyable. However, each time you find yourself getting the hang of the level and the gadgets, the game decides that you've become dangerously close to having too much fun and decides to throw a half hour stream of cutscene or boss battle at you. The boss battles are well done, but don't give nearly the sense of freedom that the levels do. In the end, the game is probably about 70-80% cutscenes or boss battles.
Metal Gear Solid 4 is an incredibly impressive mix of cinematic gameplay and storytelling, for maybe two hours. For the other 15 hours, there is a very obvious disconnect between the gameplay and storytelling. I don't care how fun your game is; it's impossible to keep a player engaged in playing a game consistently when most cutscenes run for at least ten minutes, and many run much, much longer, the brain simply shifts from playing by that point, and you lose the feel and pacing of the game. I'm very happy I got to play MGS4, I care about the story of metal gear and the game wraps it up nicely. There are also parts of the gameplay that are nothing short of incredible. However, it also demonstrates one of the problems with a game being created by an auteur. Nobody on the dev team has the balls to go up to Kojima and say "hey Hideo, we've made a stellar game here and I just think that maybe people would rather play it than watch a half hour cutscene about how computer viruses work". Well, if anyone did say that, they should promote that guy. Also, fire the guy who decided to have Octacon preach the wonders of Blu-Ray in the middle of the game.