MGS2 is the best in the series. It's just that too many gamers couldn't get their heads around the genius of MGS2. Kojima broke all conventions with that game and instead of the player controlling the game, the game controls the player!!! and we don't even realized it!!!
The amount of layers, allegory, parallelism, commentary, postmodernism that present in MGS2, I am still digesting and discovering new things even to this day. It's like a game that gets better and better each time you gain a new perspective in life. Since I have debated about this countless times many years ago on Gamefaqs I am not going to open that can of worms again.
Sadly, due to the cold reception of MGS2, Kojima went a safer route in MGS3. I mean MGS3 is fun, bar none but the fun is like a blockbuster movie fun. MGS2 is like David Lynch fun and I love me some David Lynch fun.
In MGS4, one can tell Kojima kinda tries to get into the whole MGS2 groove again but at the same time also appealing to mainstream and sad to say, he kinda falls flat. To me, MGS4 is the most disappointing of the series, once awe with the graphics and presentation wears off.
But Peace Walker got me really excited again with the MGS series. It's like Kojima got his groove back. Despite the last gen graphics, he more than makes up for it in terms of story, acting, presentation, and I really connect on an emotional level with Snake this time, especially the last boss fight. I will even go as far as saying that David Hayter gave the best performance of his career so far. Best of all, when the game ends, it doesn't really end.
It's the best game I have played last year and unlikely to be topped this year.