Button mashing is limited to people's opinion. There aren't many games out there which I do consider button mashers personally, and no I've never been defeat in a Tekken game just because someone was using low kicks. Hell Jin has a combo in Tekken which takes 90% of your opponent's health if you can land the first blow to start the chain, that's far worse than button mashing to me. I can handle a noob who doesn't know how to play the game, I can't handle a guy who's using a an attack or a combo which will pretty much win him the entire round.
PS. Capcom says SFIV won't even be out for over a year still, so don't get too excited.
PS. Capcom says SFIV won't even be out for over a year still, so don't get too excited.