One thing though. If the marine gets to be equiped with a meltagun/plasmagun, which are really badassed weapons, then its only fair that all the terminators get their best weaponry as well, and as far as i can remeber, they had access to some quite nifty weapons themselves. As shown in Terminator 1, they atleast have acccess to plasma weaponry, so assuming that their are the equal to the marines plasma, i'd recon any terminator wins that firefight, as they can still shoot as long as one of their arms are still connected to their head (CPU). If a marine takes a plasmahit in the chest, removing the anything below the top ribs, i'd guess he would be down for it, while the terminator would still have the ability to fire back, atleast for some time