I was hoping that MtG didn't mean Magic the Gathering, might as well add Bridge and Checkers too.
A guy at work is way in to NASCAR, we both like racing in general though so we've talked about it - he is oft to point out that there are a couple of races a year that aren't on ovals, but he does accept the general criticism of "wide left....wide left....wide left....wide left". We both like F1, LeMans, etc, so it's all good.
Curling is an odd one, you don't have to be in any kind of shape to play, but the mental focus, skill level and strategy required to play with the best are immense. I agree it can be broken down to a drinking game where the score is pretty much ignored, but if you're getting at all serious about it, it gets very intense. Golf isn't dissimilar, maybe you don't need as much strategy, but then most pro golfers keep themselves in terrific shape for good reason.
American Football is a great sport, though the way it's played with the huge delays between plays and the whole lot gets tedious. It's also got a steep learning curve to appreciate it. For people new to the sport, every play looks like organized chaos and every now and then there's an exciting running play.
If they enforced some of the old rules of baseball, like the "no more than 30 seconds between pitches", it'd be improved a lot. I love going to a game, I love playing it, on TV though it can certainly get old fast.