Gladiator would take this.
1. There is no limit on the human imagination. This is how Glads is built. If he believes he can do something WHATEVER it may be...he can. Xavier can easily tell him nothing is impossible for him.
2. Superman can only go so far with his abilities. This is because although Surfer is feeding him, it wouldn't be enough to break Gladiator's confidence due to Xavier's interference and mind control.
So unless Surfer had more than like 10+ years of constant bombarding Superman with Solar radiation for him to store, Gladiator would be more powerful....and literally the only limit he could really face is the limit of his imagination. Whatever he faced, regardless of what it was...once he faced it, Xavier would give artifically and unnaturally him the confidence to believe he could overcome it....and then Gladiator would...doesnt matter what.
Gladiator wins this.