Just for some perspective, here's your post with the genders reversed:

The long and short is that I'm a successful, good looking girl who has a fairly good track record with men. I'm in a relationship with somebody who I love and respect. He is my equal in many ways, superior in several, and we are different enough that many areas don't make for relevant comparison. The only weak spot is that objectively he's not as physically attractive as me. Before him I typically dated or hooked up with men who were objectively more attractive than me, and there were quite a few of them.

We've been dating for two years, long and short distance, and he's my best friend and partner in crime. As far as I know, we're both faithful through all of this, and I'd like to marry him one day. My only concern is that lately my mind has been wandering more aggressively than normal. Turning down advances, or recognizing men who are making themselves open to me, and then turning them down or playing dumb is wearing on me a bit. Recently my buddy brought around a new man of hers who was quite handsome, and it stoked a bit of angst in me about not having someone who qualifies as arm candy.

I'm not looking to break up with my boyfriend. He's incredible.

I'm just looking for some guidance from girls who could have all of the variety in the world, or miss the thrill of getting to know new people, but don't stray or leave their partners.

If you've ever described yourself as socially awkward, have had to ask for advice in the last few years on attracting men, or have options but can't keep it in your pants, you probably lack the perspective I'm looking for.

If you've managed to successfully keep a long-term, committed relationship when you could be elsewhere anytime you'd like, I'd really appreciate your insight.

tl;dr I'm with an awesome guy but could be with multiple, more attractive men. I'd like to hear from people who have successfully kept a relationship for years in this situation.

Bad news pal, if you think you can do better and it's bothering you, your relationship isn't as great as it sounds. I've been dating my girlfriend for years and routinely get flirted with by women I meet in everyday places. I live in LA where attractive women are a dime a dozen so maybe I'm desensitized, so feel free to dismiss this since it's probably what you don't want to hear anyway.