In greek mythology, it's debatable, frankly. Going up against a god in away shape or form, even if you're not aware of it, is basically the worst idea. You sometimes have people who can best gods in something, but the only one I can think of who ever actually got away with it was Diomedes (and that was for physically wounding Apollo AND Ares). One could argue Ulysses and Heracles, but Ulysses got lost for 20 years for bragging about blinding Polyphemus and Heracles is a special case in my opinion, and hardly had a pleasant life anyway.The problem isn't lack of races the problem is overpowering the Gods. IF "Has beaten gods in things' and "Gods treat them with respect" invalidates dwarves and elves.. there's plenty of "Gods don't treat humans as play things and jokes" "heroes beat gods" stories.. so.. by that logic HUMANS in mythology shouldn't be playable D&D races.
All the other examples I can think of ended poorly : Bellerophon got blinded and lost forever for figuring he could just show up on Mt Olympus uninvited, Marsyas got flayed alive for either challenging Apollo to a music contest or not correcting some random people when they said he played the aulos better than Apollo and Arachne got turned into a spider for being better than Athena at Weaving (and being a colossal smartass, although that one might have been because she knew she was fucked the moment Athena showed up). Even if you didn't ask for trouble, you're pretty much done if the gods decide to mess with you. Paris was in a no-win situation when three goddesses asked him to decide which was the hottest, resulting in the Trojan War and his death down the line and let's not even ellaborate on the Medusa origin story where she gets turned into a monster by Athena (who is definitely not a petty goddess or anything) for having been assaulted.
Again, only guy who both won and got away with no apparent repercussion down the line was Diomedes. He's like a statistical anomaly. So yeah, okay, you CAN beat the god if you're either really good, or ruthless and lucky enough, but you really, really shouldn't. In fact, you probably shouldn't have ANYTHING to do with any god whatsoever in Greek Mythology if you want to have a quiet life.
Chinese folklore, on the other hand, from memory, as it was mentioned, might be more forgiving for smartasses and usurpers. Lots of Chinese gods started as mortals I believe.