Yep I have a few ideas (including this one xD) but why do u think it's irrational ? It would mean the one that produces the highest amount of goods in a short time (and who doesnt need to sell them to survive).
My other ideas are :
-Death Match (only with other players)
-hero level
-have X kills (neutrals non included)
-the first to control a whole territory (Gondor, Umbar or Khand(+Harondor))
-the first to destroy a capital
-Death Match (only with other players, and not in team)
The 3 last would trigger the victory instantly (whereas all other picked conditions must all be fulfilled to trigger it).
Starcraft
.... xD Is it THAT good ?