The current "state of the art" propeller based combat aircraft are either things like the Super Tucano:
http://en.wikipedia.org/wiki/Super_Tucano
Or... the Predator drone:
http://en.wikipedia.org/wiki/Predator_Drone
Neither are really at the level of the World War II fighters that we know and love but they do have some unique uses and capabilities - the Predator would be sort of a boring sim tho
I know what you mean about a more what-if scenario... And you should probably watch The Sky Crawlers: