I'll chime in on this yaoi vs. yuri debate.
I hate to agree with mochi, but yaoi is rarely made as a realistic version of gay relationships. "Seme" and "uke" are well-known labels for yaoi couples, though they are not the same as tops or bottoms but more of a limiting aspect to define the character with one word and little else. Yaoi is made for girls who like to see pretty guys have sex and not much else. I like it fine, but I don't read it for the articles if you get me.
Yuri is popular in the same way: it's for guys who want to see girls make out. However, guys can get off to a dang pair of panties left on the sidewalk, so yuri doesn't even need to have two girls in love with each other. Even a hint of affection is enough to sate, as Erica Friedman of Yuricon puts it, "loser yuri fanboys". Even having one female with strong feelings for another female is enough to ignite a sizeable fire.
Now, what I said above can apply to yaoi, but here's the difference: yuri doesn't have terms for its characters. There's no semes and ukes, and while there may be some loose terms out there, they are not in wide enough parlance to really be indicative of the genre.
That's why yuri, or at least the ones I've read, put a stronger sense of character into the story. Sure, you can look to Strawberry Panic for some titillation, but that depends on how much mileage you get out of girls just making goo-goo eyes at each other. Yaoi doesn't mess around with that; it takes its characters like a man and gives them the sex.
But maybe I'm just crazy.
My point: yuri is popular more as a curiosity, a welcome fetish that has a far better wealth of stories. Yaoi deserves to be done right and taken out of the ghetto of tall guys having short guys be their lovers with evident hesitation for the latter.
If we can make these stories more realistic to actual queerky folks, we can all feel better about getting off to that rich character interaction.
Lobo, Lobo, bring back Sheriff Lobo! LOBO!