I am not asking which you prefer, or which you think is better quality at their best, I am asking which one you think would make a more epic experience if played with the Oculus Rift. 

Metroid Prime can have the best atmosphere in the industry but Halo has its pace and vehicles.

This is the only case there making a Prime 4 is okay.

Yes! I do think so and I also don't think that it would be impossible to be able to play Metroid with Oculus Rift! Cause I think that once it comes out, the Dolphin guys just might make Dolphin compatible with Oculus Rift and if that happens, it will just be fap worthy

I voted for Metroid myself, but to play Devil's Advocate based on the poll, I also can't help but imagine zooming around in a Ghost on Occulus Rift.

Metroid. It's slower paced, exploration focused, and it's focus on recreating the inside of the helmet would be amazing in VR.

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.