My apologies for the delay.
Metal Gear Solid 4 is no just a game, it's an experience.
The last game I played on my Playstation 2 was MGS3: Snake eater. That game was a profound experience as well, and I felt it only appropriate to begin the next generation with Solid Snakes last mission. It was a great choice.
The game is the culmination of the previous 3 games, and actually makes them all work together. The story is a bit far fetched, and at times silly, but it is fully realized and unifying across all the games. So all the times you've ever played a Metal Gear Solid and went "huh", they take the time to explain.
And they do it in beautiful high resolution.
As a matter of fact, the only thing that really bothers me about the game is that there were fights and action scenes that I wish I could have seen the choreographed versions. I couldn't watch Raiden fight Vamp, because I had to pay attention to shooting the Geko with my Rail Gun. I know that's a huge deal at the time to. I suppose that is what Youtube is for though!