Yea, basketball blows. College isn't too bad. Or maybe it's just because the Knicks suck.
Football definitely is great to watch once you learn some of the basic rules (which I swear to God, learned from playing Madden when I was little).
I love baseball, but I can see why not a lot of people like it. I've played it my whole life and I could talk about it all day. And nothing compares to playoff baseball. Not even the NCAA Tournament.
Tennis is also pretty damn exciting to watch. Fucking Federer is too good though... I don't really watch women's tennis; yea, some of them are pretty hot, but it gets boring after a few minutes. Men's tennis is just played at such a higher level.
whiteacid's advice is pretty good, if you want to get into a sport, find a team you like and start following it. ESPN, the sports section - you'll start picking up some stuff.