What else can be said about this one that hasn't been already said?
Graphics: Phenomenal. At times I thought I was watching a movie. The cut-scenes can be long because they are pulled off so well.
Sound: Music, dialogue, sound effects, etc is all mixed incredibly well. One of the few series that has always managed to have a good script that is performed well.
Story: One of the best, and most relevant story lines to ever grace a video game. Kojima is a master at making insightful observations based on the world today to create his world. Although someone should play the previous games to understand what is going on much better.
Online: The online is surprisingly good. It has a good following and Konami continues to support it with expansion packs that can be purchased.
The only downside is a few of the levels rely too much on trial and error. This gets frustrating at times, but in the long haul, is worth sticking with it to finish the story.
Bottom Line: If you like good games, you will like MGS4