Actually I think it generally comes down to women being able to tell what's attractive to men and appreciate feminine beauty as well. Men aren't really wired in a way to find their own gender attractive unless they happen to be gay, so as a result you wind up with the timeless stereotype of guys asking girls what women find attractive and getting coy answers.
To say men aren't attractive tends to overlook the fact that there are huge industries dedicated to selling 'hot' guys to girls even if straight guys don't get it. There is a whole industry producing Chippendales, finding and promoting boy bands and guys like Bieber (always on the look out for more as well) and the like. Girls tend to be less outward with guys in saying "I find this hot" but well, the Chippendales (or one of many, many, other male revues) come to town and the girls will be lining up to stuff their socks and straps. Even then men aren't supposed to take it all off and shake their junk around, in a lot of these shows they do, so they wear socks to take the bills (I know I've done security for a few shows like this at the casinos... and trust me, if anything the girls watching dudes are even rowdier than the guys watching girls a lot of the time).
If you want to start getting into what is considered objectively "beautiful" for a guy the best way to formalize it would be to learn a bit about competitive body building. Body builders are all about muscle definition and producing the perfect physique more than building for power and/or endurance. Those standards have been under development for centuries so they are as close to an objective rating of male beauty as your going to find, though it tends to overlook the face. A lot of these guys despite how they look also aren't that strong, the power lifters tend to look kind of fat since they build bands and slabs of muscle in many case as opposed to working for definition which is something entirely different. Pay attention to things like Mr. Olympia and you'll probably get some understanding of the aesthetics even if as a straight guy you likely won't find the guys personally attractive. If you look back at Arnold Scwartznegger and the title(s) he won when he was young, you could easily say he represents the epitome of masculine beauty (well if you put a bag over his head), of course he also used 'roids to do that at a time when they weren't as big a deal since the effects weren't well know, he came clean about this later in life especially with his heart problems, and has apparently been pretty big on speaking against them now that more is known about them, and he's really feeling the effects.
The point here is that I think it's pretty even, it's just that for straight guys their own gender is basically invisible, to the point where it's even become a comedic stereotype.
While I won't argue the truth of it or not, since it would get well off subject, but some people have argued that men and women are very different on a lot of levels. One of those ways is that while most men are just flat out straight, most women tend towards bi-sexuality which is one of the reasons they can so easily recognize and appreciate (or get jealous of) beauty in their own gender to an extent most men can't. It's been argued this might very well be a survival trait since once a child is fathered a man doing his duties in terms of hunting, fighting, and enduring the dangers at a basic level could very well be killed, being able to pair up with other women to provide a pair of parents to raise a child can represent an advantageous instinct. Of course I'm not saying this is true, and will be the first to point out it's controversial, as you have a lot of women offended by this allegation by gay organizations, and of course others insisting that any such thoughts only come from pervy straight guys who like to watch (so to speak). It's not worth having a serious debate about, but I mention it simply because the basic idea comes down to explaining things asserted in this thread.
Also I'll be blunt, I think hot girls are actually a lot easier to replace when it comes to entertainment for whatever reason. There always seems to be thousands of them lined up for movies, music, porn, etc... if you want feminine eye candy or a bunch of strippers or whatever there are tons of places that can hook you up especially in the US's entertainment centers. On the other hand you tend to only have one or two "Biebers" per generation, and a lot of these male "talent" agencies putting on the strip shows and such seem to have a harder time recruiting and while not uncommon there are less of them. This is why it can be a bigger deal when say the Chippendales come to town, and all the ladies show up, where the same area might have numerous full time clubs providing girls doing the same things. There are full time establishments that have men of course, but they tend to be much fewer in number and there are many communities that don't have any it seems. So while "male beauty" can be defined objectively, I do think it's rarer, and also tends to take a lot of work, as much or more than hot girls put into their own beautification. Maintaining a body builder's physique can be quite an undertaking.