MGS2 is my favorite and the first I played. I really wasn't expecting such a thrilling and awe inspiring game. I couldn't turn it off and the plot twists at the end were cool. I didn't mind playing as Raiden because I didn't know anything of Snake. MGS3 was very good as well. Never played MGS 1 for ps1. I bought MGS4 but haven't gotten around to finishing it. Not sure why, the overall feel for the game and less need for stealth maybe? I'm sure I'll finish it one of these days.
You have a good point. If you didn't play MGS1, chances are that you liked Raiden and you probably liked the game a lot. Even the people who beat MGS1 liked MGS2, but not nearly as much because of Raiden, Rose, and the more narrative approach to the game. Plus, Solidus Snake was not nearly as great/memorable of a villain when compared to Liquid Snake or Liquid Ocelot (MGS4).
@Anarchy West- Metal Gear was not included as it was not a Metal Gear Solid game.