Yeah, but the undersized "quick" guys are a pretty high bust ratio. They get by on speed and are strong enough to beat college lineman, but then they get to the NFL and they're overmatched by giant interior lineman and their speed is less useful. Add that to the problem of most of them not having great technique because they've been able to get away with it up to that point.
Obviously you're going to have freaks like Suh or Ngata who are stars from day one. Guys who can both rush the passer and hold ground on double teams and play two gaps. Fairley is not that kind of player in my opinion. Again the drafts for the past 7-8 years are full of guys like him who dominate in college and then just disappear. When you look at the successful ones, they're more the run-plugger types or guys who weren't of such high reknown in college because they were busy freeing up the other guy (Kyle Williams has turned out to be a better NFL player than Glenn Dorsey, for instance).