As far as I'm concerned, unless it says Grado or Sennheiser on the side, it's probably crap. Can't blame the other manufacturers though, people want headphones that dump bass and don't care about highs and mids. So they put crappy speakers in the cans and spend lots of time making adds with rap dudes who look like they're scowling.
Wouldn't buy skullcandy though. If I wanted cheap headphones, I'd go for a Sony or Koss pair. Don't see the point in it though, when you can get a great pair of headphones from Grado for under 100 bucks. Sennheiser seems to have something at just about every price point, and all are probably above average in sound quality.
I have a pair of SR 125 grado phones. Best phones I've ever listened with. I bought it after I wore out the ear muffs on my SR 60. There really isn't much of a difference between the two.