For that matter, hyenas aren't really considered "big" hunters, traditionally.
Baboons are very good to, if rather malicious about it. And, believe it or not, Argentinian wild boars are supposed to be very successful hunters...not just in their success rate, but in the size of their kills. They're supposed to be a big problem for cattle ranchers in Patagonia.
And at this point, I'd dispute the idea that man's an exceptional hunter. How many people do you honestly think could survive having to hunt and kill their own meals these days?