I think that the funnest sport to play and to watch is basketball. Its much faster pace than a lot of sports such as soccer or American football and the action never stops. The only down side to basketball is that lots of baskets are scored throughout a game which makes each one less exciting unlike American football or soccer where each touchdown and goal is a huge turning point in the game.
I've played them all, football, baseball soccer, basketball, and hockey and for me hockey is the most fun to play.
to watch I enjoy football (NFL) the best.