I guess it depends on how much you focus on combat.  Hmm...what system works for solos...  Well, does there need to be a possibility for character death?  Do you object to a system in which the GM probably does an equal amount of roleplaying as the player?  If not to both of those, I'd probably try to jury-rig With Great Power for a more fantasy setting...wouldn't take much.  I guess it depends on how much you're into the stats/numbers aspect.