Metal Gear Solid 4: Amazing visuals, perfect gameplay that can be played in multiple ways, Hollywood-like production values and the end to the most amazing saga ever. Plus, this game made Snake truly legendary! The game also has some amazing moments, like the microwave scene, the slow motion sequences during the act 3 chase, all the boss fights, the battles in act 1 and 2, playing as REX, the graveyard scene, Otacon's explanation to Sunny about what happened to Snake, and there are so many more, I just can't remember them off the top of my head, it's 3am here :P. Anyways, for me this game will truly be the greatest and no game in the future, not even another MGS game can be as good as MGS4 for me, mainly because Snake will be absent from them. I doubt anyone can create a game with a character as compelling as Snake.
