The only cousin I have whom I'd consider even remotely attractive is adopted (I'm white, she's Korean), so don't think that could count as incest.
(Most people seem to find one of my other cousin's more attractive, but I never have, perhaps because our personalities don't mesh so well. She looks like a taller Julia Roberts, which to me makes Julia Roberts unattractive as well.)
From a biblical standpoint, it seems reasonable that what counts as incest would change as time goes by. Adam and Eve's children would have to mate with their own siblings, but the mutations causing the genetic disorders that make incest risky would not yet have occurred, so this would not be harmful at all. A couple thousand years latter there were defects enough to warrant some regulations against incest, but 4 thousand years latter much stricter regulations would be appropriate.
It would also probably vary based on the genetic diversity and prevalence of genetic defects among the society. I believe I've heard that unrelated Native Americans from anywhere in the Americas are all genetically closer to each other than fairly close (but probably not first) cousins from Europe or Africa. In general, Native Americans are less diverse that Asians, who are less diverse than Europeans, who are less diverse than Africans, but the least diverse races actually have far fewer genetic diseases than the more diverse ones.