I don't know much about Master Chief so I can't say anything about that opinion of yours, but even so, as good as every cinematic I've seen with Master Chief involve epicness to a lesser or greater extent. Lesser or greater, there's always epic around.
Then there's the coolness factor at armor and attitude. The fact that he's breeded to be thrown into an enemy army and manage on his own. And there's the epic infinite of destroying a starship without one of his own 😛
Each and every dialogue is pretty epic as well (If you ask me)