I would say I prefer (american) football is the most enjoyable to watch, especially college football. Going to a college football games is one of the most enjoyable things to do, in my opinion, probably because I am attending a university right now and I am a die hard fan of the team.
I also like basketball, baseball, and soccer is starting to grow on me. I don't think it will become my favorite sport to watch, but I have found that I am finding it more enjoyable than I used to.
Lastly, this term I am taking a Team Handball class and it is an awesome class. I had never really heard of it before I signed up for the class, but after having played it a few times, I really hope it becomes more popular in the US because it is really fun to play.