Would you mind posting a general descriptions of their powers? (were trying to push for that to become an official rule of the battle fourm) anyway i'm familiar with spaceghost, and most versions of megaman (x) Space ghost should win this fight. He has the ability to Turn Intangible, which should neutralize most of megaman's attacks. He also has the ability to convert his body into pure thought, appearing anywhere at will. His invisible belt, would make it hard for megaman to realize where spaceghost is, and allow spaceghost to appear behind him. Space ghost's force field is powerful, as demonstrated when he touched the Surface of a yellow star. for the time being i will also assume that their blasting power is roughly equal( i belive that SG also is higher in this category, but megaman doesn't show enough feats for me to be sure). But what i believe is his biggest advantage over megaman is his unhampered ability to fly. While x has fought opponents that could fly before, none of them were as fast or as agile as space ghost
heres a little info there is more on his powers but i need to find him.
According to wiki, Space ghost has “Invisibility, teleportation, flight, enhanced strength, Power Bands give an assortment of energy powers and abilities”. His band’s are surprisingly very powerful. His “freeze field”, for example, has protected him from 300,000 degree lava(2). This guy casually flies through space, and although I affirmatively say he can travel at FTL speeds, he has to fly pretty fast since he manages to catch up with (and sometimes surpass) his FTL spaceship. He also has his 'viso penetron beam'(1), which is like x-ray vision (permits him to see through dense objects). He also managed to temporary stabilize a planetary core(3).
I think Space Ghost would win but at least Megaman X would put up a good fight. Remember that he fights enemies who turn invisible, frost abilities, and high advantaged but Megaman still wins. But in the end Space Ghost will just unleash a devastating attack.