The villains being considerably outnumbered kind of lowers their chances.
The two weakest of the villains are almost definately Lust and Gluttony, definately Gluttony, who despite being very powerful, is also kind of a stupid retard who does not keep himself from "dying" adequately, so he should be first to be taken out, well, the first Homunculus anyway.
Wrath and Kimblee are easily the two most capable on their side, Wrath being the best pure physical combatant in the entire series, and Kimblee being the most destructive alchemist whose name is not Hohenheim or Father.
That said, I don't think they would be able to overcome the fact that the heroes outnumber them, Kimblee is by his own admission physically out of shape, one good hit from Armstrong, Greed, Scar, or Roy would take him out.
There is also the matter of most of the team being unable to physically harm Greed when using his full armor... Which for some reason he rarely did in the series.
But yeah, heroes probably win.
The villains win. Gluttony is most definitely NOT the weakest, rather the most powerful the villains have. Kimblee is the weakest, he got owned in all of his fights. Not to mention Wrath is a ****ing beast. Gluttony using his portal of truth can take out most of the heroes though, and between the rest of the villains it'll be easy enough to wipe out the others.