I don't think I'm handsome, I know I am. That's the difference, confidence comes from knowing that you're good looking. And not worrying what others might think of you all the time.
So do some people look at me and think "not bad"? probably, I have some evidence to back it up too, since I've had the chance to actually say to a few girls that I don't desire THEIR company.
I think I don't fit into a specific niche or anything though. I'm just generally good-looking. Good structure, high cheeckbones, strong jawline, blue eyes (always in demand), synched eyebrows, teeth that are in a perfect line and a distinctive straight nose that is just the right size.
And I keep my hair short to avoid that creepy long haired weirdo-look that is always so nice to have. (spot the sarcasm)
The fact that I can look at myself in the mirror and say; gee, that looks pretty good man, does wonders to the ego. I wont lie and tell you I'm a bodybuilder or anything, but as I said, with a little self-confidence and good clothes you can go a long way without actual muscle. And it's the confidence that gets you respect, and respect gets you women.
Some, self-awareness helps too.