Just a little something. Metroid Prime is not an FPS the same way Half Life and HALO are. MP is something quite different, even if it's on the first person view.
But it's a tough one anyways. Master Chief is THE BADASS, but so is Samus.But Master Chief can not turn into a ball or put power bombs or freeze enemies or super missile them, etc. And he can not make two jumps in the air either. Although we still have to see what can he do on HALO 2
But Samus gets my vote for default anyways, since she's such a hot chick in such a hot suit