doom guy is faster, but master chief has better training and arguably better armor. If its in a long range shooting match, master chief might win, but if its up close, doom guy destroys him. Then again since master chief has really good reflexes, he might be able to react to doom guys speed but I doubt it because we see doom guy in the games melee kill demons 4 times his size, so I don't think master chief stands a chance there.
to summarize master chief probably wins in a long range gunfight but in a melee match doom guy wins.
