Dragonball and Dragonball Z are the first that come to mind. They fit the American comic book hero theme better than any other anime I've seen, and would transfer perfectly to american animation. Plus, all the filler could be cut out (except the good stuff, like Bardok).
Also, I wouldn't mind seing an American take on a Pokemon story that was closer to the manga. Then again, I also wouldn't mind seeing a Pokemon anime that simply followed the manga.