I have been playing this new game called Civilization Revolution. In this game you start with one city and you explore the world, research technologies, expand, fight wars, and there are four ways to win:
1. Conquer everyone
2. Build a "World Bank"
3. Build the "United Nations" (I think this is an evolved version that's actually a world government)
4. Colonize another planet
To win the 4th way you have to be scientifically advanced, have the industrial strength to build a space ship, and then wait.
I think there should be a 5th way you can win, and that's to invent time travel. At first your time travel would be pretty primitive, but eventually you'd be able to see the future and use its technologies in the present day, or travel to the past and change things to your advantage. That, to me, clearly makes you the winner.
Even if you believe in the "alternate universe" theory of time travel, at least you'd be changing things to your advantage in that other universe, which is still a victory. If it is an alternate universe, you could give them time travel technology and give them instructions to travel to another one and do what you've asked until eventually someone else would travel to your universe and do it to yours.
Any way you slice it, you'd definitely "win" the game if you invented time travel.