Just once I wanna see an RPG where you bring the world to the brink of destruction. Strictly for variety, see. Also, it'd make a lot more sense, having this infinite army of rather pathetic sorts fighting to save their planet rather than destroy it.
How about a Hobo RPG? Nothing particularly cosmic happens in the plot, but you get this nice plot arc of going broke, losing your job, and trying to escape to a country with better welfare services, and to this end you ride trains, wander the countryside, steal food, get drunk/stoned (to regain health points), expose yourself to women and children in the park (for entertainment), stab people in alleyways, and otherwise engage in typical hoboish activities.