And yes, it is sexist. When was the last time you saw a male character in a gaming manual who was dressed like that? (And no, I'm not talking about a barbarian in a loincloth. I'm talking about a guy wearing an utterly impractical and inappropriate outfit that's clearly designed to draw attention to his very large package. Think male stripper.)
Edited to add: Yeah, those links in Jonesy's post. The last one in particular. That's what I'm talking about. How many outfits like that do you see on men in gaming books?
But the male "package" isn't as universally considered as sexy as female breasts or legs. Again, it's DIFFERENT social standards. My girlfriend and I agree that genitalia is not nice to look at. We also agree that breasts are very nice to look at. My friends will generally agree that the upper body(chest, arms, face) are more attractive on men than their junk.
EX: the 4e dwarf image, shows the dwarf female with nice cleavage, and the male with a nice exposed bicep. Almost identical imagery is repeated in the Elf, half-elf, and human artwork. The men also have strong, sharp faces. These are the qualities that are found attractive in men, so they're emphasized.
Not all girls go crazy for David Bowie's crotch-rocket.
continuaing with 4e Players Handbook examples of male sexiness:
pg58 we've not a nice shirtless tiefling.
pg72 we've got a dwarf who's musculature is clearly visible through his chainmail
pg103 we've got an elven woman with some nice side-boob and enough swords to show she's sexy, yes, kick ass, hell yes.
pg116 we repeat the "sexy bicep" imagery on a man.
pg142 we've got a dragonborn female with a low-cut breastplate but beyond that it's realistic armor and on 143 we see the "sexy bicep" again.
pg176 we revisit our sexy male tiefling's bicep
pg201 we get some sexy dragonborn arm muscles
pg203 we get a elf-fighter in some nice form-fitting mail, sexy, but practical
pg213 we get a variety of armor diagrams which I think are interesting and useful.
a: cloth is male and shows off the arms
b: leather is female and shows cleavage and abs
c: hide is male and low-cut and armless
d: chain is male and short-sleeved
e: scale is female and practical(showing off a bare arm)
f: plate is male and practice(showing off one bare arm)
pg224 is a very practical female fighter
pg226 repeats practical female fighter
pg234 we have a woman in sexy leather, but she's also about to stab your face.
pg235 we have a shirtless dragonborn with a VERY nice chest
pg258 we have a very sexy woman but very practial outfit
pg273 gives us another sexy man-bicep
pg294 gives us sexy dragonborn man-arms
And the imagery goes on and on. Now, the two points I'm trying to make here are as follows: You guys can't be using stuff from 2ed to talk about sexism. That was roughly 15 years ago, and the imagery has changed because the content creators have accounted for this.
My second point is that what is considered sexy for men and women is different. Your average man will generally find(of the unenlightened body parts), legs, breasts, hips, butt, and stomach attractive, so shots of women will show off these things, it's genetic, they're looking for fertility. Women conversely are going to find depictions of strength and grace attractive(again, it's biology), so you get muscly arms, chests, and sometimes legs shown off. Biology doesn't care if you've got a big package because the package doesn't help you kill a tiger for food. Likewise male biology doesn't care if you've got a nice lady-part but will if you have nice breasts/legs/hips because it looks for fertility.
No we're not Neanderthals, but the basic biological instincts are still there, the imagery is the way it is because at our very base, it's what we want.
That's "WTF is this guy's problem?". Except more politely.
