The only thing Halo has going against it, is it's popularity with the online competitive community. In my mind I just can't see that kind of fast paced multiplayer action working well with the first iterations of VR, which assumingly wouldn't be able to keep up with what the players expect.
Metroid on the other hand is solely story driven and given its dark extra terrestrial atmosphere would be fucking awesome playing first hand through Samus' visor. I do enjoy both franchises honestly, but for Virtual Reality I give the nod to Metroid.







