Turns out it was almost as long as the first two chapters of my undergraduate thesis. THAT is how much I want you to want to buy and enjoy hot sexy eroge. I congratulate (and apologize to) everyone who read the whole thing. You have earned my eternal gratitude and respect.
If you TL; DR'd on me (I don't blame you), here's what you need to win half the battle:
*The best way to encourage more diversity in content and game design is to start embracing game designs that don't conform to known genre conventions, or to start accepting and validating new genres entirely.
*Eroge are mainly about text, storytelling and talking, making them different from most games we know. To acknowledge them will help encourage developers that might wish to construct games along those lines or with similar themes and foci.
*The focus on character interaction makes eroge friendly to complicated, initially vague cast members who need a lot of exposition to get to know.
*Since the only real way to "fail" an eroge is to hit a BAD END or accidentally hook up with the wrong girl (it can happen), there's no way eroge can be accused of being "too much like work," a common complaint by non-gamers being asked to get into the hobby.
*An eroge's lack of conflict-based gameplay makes it more receptive to traditional, more passive storytelling methods, and keeps it from getting "fat" with grinding in the middle, which sabotages most game plots, while making their appeal easier to understand for non-gamers.
*The eroge's rigid, first-person narrative structure forces a player to connect with protagonists that might be otherwise be unlikeable, making it easier to cover difficult subject matter while discouraging players from treating in-game choices shallowly.
*Eroge can be built on the cheap, but will be hard to market widely because of the "porn with plot" stigma, among other things.
*Sometimes an eroge's copious amount of descriptive text can underline the limits of graphical realism, exploring heights of violence or gore that might sicken even the most hardened shooter veterans. Take the vivid text from Fate/stay night's first BAD END, where the protagonist describes himself being killed in a rather horrible fashion. And Fate isn't even a horror-themed eroge.
I would also like to acknowledge, as was pointed out by a few on Japanator, that my use of the term "eroge" isn't exactly helping my case when I claim that they're more than porn. However, I will continue to use it because the word is in my blog header, and because others don't like it when I use "bishoujo games," thinking it an unnecessary insertion of Japanese words SUGOI SUGOI KAWAII -SAN DESU DESU. Eroge is still one of those words, but it's slang, and sounds nicer.
As a reward for those who didn't TL;DR this time, here's a Nazi SS Battle Maid. She has pistol-blades, wears a jetpack, and hides grenades in her bloomers. She's not an eroge character, but very well could be. She (and her peers) are among the only good things to ever come out of Nazi Germany. Well, that and maybe the trend of girls in saucy military outfits.