1) NFL - between the playoffs (always exciting), the Super Bowl (biggest single event in sports), and the Draft (huge offseason draw, IMO), I think pro football takes it. There are changes I'd like to see made, and other changes I wish hadn't been. At the end of the day, I'm willing to watch most of the games, regardless of whether 'my team' is playing or not.
2) NCAA Football - Football is and always will be the top banana, and for me, the only question is which I truly enjoy more, pro or collegiate. I give CFB all the credit in the world, but taking into account the BCS and annual/inevitable/aggravating bowl game snubs, I've got to give pro the gold.
3) NCAA Basketball - The tournament kicks ass, period. NCAA Basketball also sports the most reputable and fun-to-watch/follow dynasties (Duke, UNC, etc.). The sheer volume of teams competing takes away from the regular season, I feel, but it all gets wrapped up nicely by March. If I didn't love football so much, this might be #1.
4) NBA - A lot of people don't like the NBA, and I know why. I don't like those aspects either (money grubbing, bad attitudes, etc.). Still, they're the best in the world, and that counts for something. I also really enjoy the recent influx of foreign players - Andrei Kirilenko is the coolest man alive. If Stern would grow a brain and change the All-Star game format to USA vs. World, this might leap into 2nd or 3rd on my list.
5) MLB - Sitting down and watching an entire game on television is still hard for me. The game seems to move slower than a one-legged geriatric who just took his daily medicinal J to the head. Nevertheless, MLB has history working for it, and there are always intriguing stories. Hitting streaks, player movement, the size of Bonds' biceps, the length of Damon's hair, etc. The World Series is usually pretty good. Playing fantasy baseball also helps.
6) PGA - The Masters, the US Open, and the Ryder Cup are all worth watching. Outside of these (and a few select other) major events, I can't really stomach it, even if Tiger is setting some amazing record. If golf had more personality (maybe have more stuff like the Skins Game more often?), it'd be a lot cooler. But not cool enough to supplant MLB.
7) Boxing - Boxing is a farce these days. There are no cool boxers, not like when I was a kid. No more Tysons or Holyfields. Just sissy English asswads who deny people the rematches they deserve. Every once in a while, it seems, there will be a fight that really captures my interest/emotion (Lewis/Klitschko, obviously), but by and large, it sucks. Even so, it beats the hell out of...
8) NHL - I just can't stand it. The games move slower than MLB games, and the teams aren't interesting. The last time I followed hockey at all, it was when the Blackhawks had Eddie Belfour, Chris Chelios, Jeremy Roenick, and Tony Almonte. Each of those guys has since played for multiple other teams, I believe, and that was just six or seven years ago or so. Just as the NBA's increasing number of foreign players helps its appeal, I feel the staggering number of foreign players in the "N"HL hurts its own.
9) MLS - I can't even speak intelligently about pro soccer. Freddy Adu's fourteen. Cool. Call me if he thinks about becoming a cornerback. (Note: If I lived in England, I bet I would watch a lot of Premiership football. I've caught a few games here on Fox Sports World, and those guys are just fun to watch. I do not, however, live in England. So.)
10) NASCAR - Fuck NASCAR. You wanna know why NASCAR draws so many people to it? Because you can drink a shitload of beer and hang out with other inbred dickless rednecks. There will never be a shortage of either, so on it will go, in a pointless, endless circle. Just like the races.
Others: I can't watch tennis. I would definitely like to see Serena Williams take a riding crop to Anna Kournikova's arse, but none of that has anything to do with tennis. Men's tennis is the same as women's, just without the sex appeal. I respect what they do, and it's still better than fucking NASCAR, so I guess it's not fair to put it down here, but whatever. The Olympics suck. Can't remember the last time I gave a single shred of shit about anything going on in the Olympics. It was probably back when that whole DAN vs. DAVE thing was going on. X Games... ...eeuuggghh. That's all I have to say about that. Can't really think of anything else right now. I will say this - the World Series of Poker and MXC (if I felt right about putting them on the list) would probably be sixth and seventh, respectively. Both are a lot more exciting than everything below MLB.