Quite frankly I couldn't compare Halo to Metroid Prime... Simply because they are in different genres. Much how I would not compare Zelda to Final Fantasy... But thats me.
Metroid Prime is a First Person Adventure... And if anyone has clocked an hour or more with it, then they will know that its not like a FPS... Hell at times it feels more like a platformer than a FPS <g>
Seriously though you couldn't compare the two as they both have different control schemes to deliberately distinguish between the two genres. Add that to the totally different goals and objectives in gameplay and the abilities you have within the game (morph ball, boost ball, spider ball, grappling hook, various suits etc etc).
For anyone to really compare Metroid to Halo would be incorrect IMO as they both stand tall in their own given genres.