Tough to say. If I could pick ANYONE, I'd pick some of my player-created characters whom have been engineered for greatness, and all have probably saved the world already. It would range from Oblivion to Fallout to Demon's Souls to Saint's Row 2 to Mass Effect and everything in between. If it had to be a non-customizable character... hm.
Harry and his bucket full o' dinosaurs!
Jk. He'd be the first to die.
Tali, Garrus, or Legion from Mass Effect for her/his/their intelligence and experience in combat.
The Prince from Prince of Persia (Before he became angsty and listened to Linkon Park), since he'll always be able to traverse all terrain and save those in danger.
Lastly, probably Solid Snake before he became old. He was fast, a good shot, spoke a ton of languages, high IQ like the first partner, and could carry out orders well. Explode something? Call him. Kill someone? Call him. Escape? Hide in a box and call him.
And with Ma-ti, with the power of heart, we create... CAPTAIN PLANET!