I'd be inclined towards a superhero system personally. That means that half a dozen people will be here to suggest Mutants and Masterminds before the day is done, but I favor Wild Talents. The various ORE games all interconnect okay (at least as well as the various d20 games do, for reference), so there's also an option involving a bit of patchwork between Nemesis and REIGN if you want modern fantasy where the fantasy powers are more in the vein of spells and fantasy combat than superhero stuff.