Used to get to go to 4 or 5 Bullets/Wizards games a year and the seats were not even ten rows off the court, I thought it was absolutely awesome. The athleticism of these guys up close was insane (although I am sure that's how the other pro leagues are too). My favorite live sport if the seats are good, and I generally strongly prefer football to basketball.
Don't know anything about hockey but have been to a couple games, really liked that as well. Very fast paced and was enjoyable even with limited understanding of what's going on. It's nice how they don't have as many stoppages as the other sports.
Baseball - fun if it's not too hot outside, felt really slow to me but can be nice if you embrace that aspect. Was able to go to a few AAA games and the play seemed decent, and as a bonus tickets were like $6.
Football is my favorite sport by far and the only one I follow all that closely, but actually my least favorite to watch live...I feel like it's hard to get a seat where you can both tell what's going on and also see everything happening at once, if that makes sense? I'm also a Redskins fan and I found the Fed Ex experience to be pretty bad, that seems to be a pretty popular opinion. I strongly prefer being able to watch games on TV and have redzone on as well and track all my fantasy scores.