Depends on the situation. I compare myself with some others when there's a good reason to--pickup volleyball games go better when both height and skill are roughly balanced between the two sides, for example, so I keep in mind height. When I was pressed into playing ultimate frisbee ( a sport at which I feel I suck), I'd look to see who looked like the better runners. Etc. But I'm pretty sure that's not what you're asking about.
For the most part, no, I don't. I know that my metabolism, bone structure, and build when I'm not actively trying to control what I look like are very different than those of most guys, and pretty much always have been. I'm long used to the idea that no matter what I do, I won't look like almost any of those guys, and that the specific ways they went about getting to where they are wouldn't work for me. And I'm not a size queen, so my ego doesn't depend on my having a smaller waist, broader chest, or whatever other measurement you want than that other guy. I look at attractive men and mentally respond pretty much with something along the lines of "He's hot" (or not), and whether I think I have a chance at having a conversation with him. So to the extent that I compare my build with his and see if he's physically out of my league, sure, but to that extent--doesn't everyone?