I'm not sure what archeology has proven, to be perfectly honest with you, other than the fact that Troy was, in fact, burned around about the time the Trojan War was supposed to have taken place. There's a lot of debate about the details, though. Is Troy VI the Troy of the Trojan War, which would jive fairly well with Homer's account (more or less?) Was it destroyed by earthquake and subseqently razed by the Greeks, or was there actually a Trojan horse or not? Or is Troy VI not the Troy of the Trojan War at all, and instead Troy VIIa is the one? If so, that doesn't jive very well with Homer's account, and it makes the Greeks little more than pirates who preyed on an already beseiged and downtrodden city. Were there really any such people as Menelaus, Paris, Helen, etc? Was there even a High King at Mycenae capable of marshalling the Achaean Greeks into an army? Where does the neighboring Hittite Empire fit into this, since Troy was arguably a vassal (or even a satellite city-state) of the Hittites? I've even seen conjecture that the sacking of Troy was a move in a "cold war" between the Myceneans and the Hittites.
There's a good book (and BBC video series) about Troy by a fellow named Michael Wood that explores a number of the possibilities. He's clearly in favor of Homer's account being as historically accurate as can be, so he looks for evidence to support that thesis. Everything he finds is circumstantial at best, though. At the end of the day, we know very little about the Trojan War and can't even firmly declare that there was one, so everything about it is legendary by default.
Granted Troy (the movie) can be done (and I hope it will, actually) as a historically-styled movie, with things that are all reasonably possible regardless of whether they actually happened or not. I suppose maybe that's what posters here mean when they call the movie "historically accurate." Actually, I think that's the movie I'd most like to see, everything else being equal.