If your going to judge things by cartoons, then Mace Windu can knock out a half-kilometer sized Seismic tank, can take out half and army of super battle droids with his fists, and can essentially fly. Yoda can bring down four giant Separatist droid and ship carriers, and Shaak Ti can fight off twenty Magnaguards. You'd have to superpower every Star Wars character in the show.
Because it was in the cartoons that Grievous defeats five Jedi; he does it against crap Jedi in the books, and it is mentioned that he defeated some Jedi on Hypori, including Shaak Ti. I'm merely saying that if you consider Grievous' power in the 'toons, you have to do the same with everyone else, too. Not to mention it is weird when compared to the movies, but whatever.