It would be either one of the Overlord games or one of the Fable games.
If it's one of the Overlord games, I just kill everyone and rule the world.
If it's one of the Fable games, I stock up on Resurrection Phials (for those who don't know: they resrurect you when you die) and health potions. Buy and rent out every bit of real estate and sleep on a pile of gold (not literally, because gold is way to hard) for the rest of my by potions made infinite life.
I'd also get an undead girlfriend (Lady Grey).
I'll probably kill that weakling Lucien somewhere along the way.
And then I'd rule the world.
EDIT: It could be one of the Pokémon games though...
This thread kinda reminds me of the Legend of Neil...