The answer to that is pretty much rooted in what everyone else said. The multimedia of the world is what gives us the image of these guys. Not that there's anything wrong with them. I mean, why should you feel ashamed in finding a model attractive? We all have different tastes.
But I do think it can get out of hand if the guy expects every guy he talks to, to look like the models in magazines/tv. I think you would set yourself up for failure unless you were "equally" good looking as them.
Honestly, while I do enjoy looking at some of the handsome by default models/men that the media spews out, I like normal guys too, especially the ones who take of themselves. Same with race, I don't find one better then the other. I find beauty in all of them and I love diversity.
The way I see it. It's like this. I have a thing for bodybuilders. However, I'm not attracted to the ones on the fitness magazines and competitions (the whole ultra defined, vein look). I'm much more attracted to the off season bodybuilder. While people like both types, a big lot would want to go for the vein/ultra defined one. Also with face. Sure, I can admit when I guy has a nice face like take... Hmm... I can't think of a good example of who to use at the moment. lol I guess Brad Pitt. All girls and a lot of gay guys find him incredibly handsome and sexy. I do think he is handsome but I'm more into someone like Taylor Lautner (I've used this example a lot I realize lol). I think the point I'm trying to convey is that I don't necessarily look for perfection. I think a guy with a bigger nose isn't "ugly" or a guy with brown eyes looks dull.
Anyway, I rambled. Back to the question, it's really just the media. This is especially impressionable on kids and teenagers like how Mickey said.