This is the first I'm hearing of this.
DOC THE DELOREAN WORKS!!!!
Anyway, I think this is the common perception and it is sort of true, sort of, but not really. I'd say it's about equal. There are gays who only care about looks and those who care more for personalities and other intangible attributes. I think a lot of gays are interested in fashion, and gays are usually represented in the media as feminine, but I wouldn't say this is the majority. Straight society is just as vain. Women wear tons of make up, guys still try to make themself as sexy as possible, and in front of women many straight guys I know act ultra macho, which is as appearance. If you are comparing just gay men with straight men, then yes gay men are probably more obsessed with appearance. However comparing straight society and relationships as a whole with gay society and relationships I'd say it's about equal.
Of course about 90% of the world is straight, so straights are quantitatively more obsessed with looks, simply because there is way more of them.