Is it just me? They also have basically the same position in the game by the end. They are the captain of the big awesome ship that is supporting the protagonist. --- ~ IN THE FUTURE there will be no black people and white people. Just robots.
Nothing would bring me more joy than personally crushing some Zerg skulls with the Chief.
The Tyranids are a better implementation of the concept, but both of them are kind of lame. They are both so overpowered in their respective universes that they always have to be defeated by means of deus ex machina. --- Perfection. Where everyone fails. If you expect nothing you can be happy for everything.