The problem with FPS as a spectator sport is you can't see everything at once. You only see through the eyes of one player at one point in the map. Also, with the exception of 1v1 games like quake live, watching a top level FPS player just isn't that impressive. I can watch the world championship of counterstrike and other than aim, I don't see what makes them so good, even though I've played a lot of counterstrike and understand the game well. I don't know if that's because the game just doesn't have that high a skill ceiling or if it doesn't show. Same with Call of Duty. With MMOs like Wow it's hard to see what abilities they're using visually and I honestly don't think there's that much skill in it. I can't imagine watching a Wow arena match and being amazed at how good a player is.