Well, assuming that the "Hades" wasn't put there simply for looks in the cutscene, but was an actual ship, let's think about this one. First of all, the Hades is 3Km long... A ship that big crashing into a world would either A) disintegrate instantly on impact, as the sheer force of impact would basically liquidate/destroy everything for miles around. or B) not be crashed on a hillside, but span SEVERAL hillsides. 3Km is over a mile long.
So, if we're not talking about a Hades, then what could this possibly be? Well, looking though pictures of other FS1 era ships, it could be an Apollo that is on it's side... that's 21m long, making it a good 60+feet. Also, we're told in FS2 that Deneb is inhabited... Cygnus Prime. The Vasudans flee because of the NTF, but did the Lucifer bombard? and if so, how were they able to recolonize when Vasuda Prime was rendered uninhabitable. If the Lucifer did not bombard, what are all those alien bodies that look like infantry doing on the ground? Do we know if Cygnus, or any other Deneb system planet was ever inhabited by the Ancients? If it was, that could be an Ancient ship that's crashed there. I admit, that protrusion coming out of the wreckage isn't repeated in very many ship designs. It can't be an Anubis, and it doesn't look much like a Valk, but that is a small possibility.