Considering this is the game forum, we go by what was done in the game. In the game, Chief isn't a god, his shields go down faster then Shepard's, Shepard has better weaponry, barring the Spartan Laser, Energy Sword, and Gravity Hammer of course. He has better shields, and his biotic powers are a stomp for him.
Now if you want to argue book feats, we can go there, I haven't read the 2nd and 3rd Mass Effect books, but if Shepard's in them, we can use him.