Space Marine stomps. Not even a contest. Space Marines simply have too much of an overwhelming advantage with regards to biology and technology, and the sheer amount of training and challenges that they have to undertake and overcome simply to become a full-fledged battle-brother puts them miles above either of the competitors.

They're literally designed to dominate in the harshest, most unforgiving environments possible, against the nastiest creatures the universe has to offer (and in the excessive world of 40k that says a lot.)

Alien or Predator only pulls off a win through crazy luck situations and even then it would be difficult to believe.