Don't fall victim to the childish notion anime and also Western fiction often try to propagate: That heroes form one group and villains another. While heroes might actually do that, a villain's worst enemy isn't singularly a hero. A villain can't ever trust another villain either, because otherwise they wouldn't be villains in the first place. Two heroes might compete on who's the bigger hero, but they wouldn't like to risk the evil winning due to their competition. However, a villain would care nothing for such a thing. Another villain eliminated is one competitor less.
Besides, Sasuke is a questionable villain at best. He might want Konoha gone and isn't adverse to involving others to see it done, but there's no indication he would want to be the emperor of the world or the world to change beyond recognition. As long as he doesn't pull of something really evil for no good reason, I'll see him as an anti-hero. He considers Konoha a nest of evilness, which is why he wants to destroy it. It's not like he would admit Konoha is a nice enough place and he simply wants it gone because it annoys him or prevents him from performing some grand experiment. He wants to destroy Konoha because Konoha is the villain for him.