What did Capcom and SNK bring to the fighting game genre?

Street Fighter II brought kara/whiff canceling.

didn’t darkstalkers invent pursuit move on grounded opponents ? i miss that shit

No, pursuit moves were from VF1, although they were appropriated from scrolling beat em ups (stuff like X Men 6 player arcade game) I’m pretty sure VF was the first 1 v 1 fighter with hit 'em while they’re down stuff.

Simply among the first fighting games, nothing more. As for SNK merely the same thing with a hip hop sort of theme.