Thor is a demigod, and species doesn't really matter.

From everything i remember, thor was not the offspring of a god and human. And when concerning a god vs alien, yes it does. If it was a god/human vs god/alien, im sure it would play a huge role.

Gods are aliens too, y'know. And Marvel's Thor is half aesir, half elder god. Hence, demigod. Doesn't really matter though, since Thor still isn't fast enough to take Superman.