I’m not saying that Gladiator, as defined, couldn’t paste everybody. I’m saying I hate him & want to see him brought low like the Witch-King. He’s full of himself.
Overall my money would be on Majestic as he may be an arrogant dick at times, but he is (judging by what I 've read) by far the oldest, quickest thinking tactically, most intelligent, and most ruthless (re killing outright vs trying to subdue) of them all. Possibly Omni Man is as (or more) ruthless, but his overall power set doesn’t come close to Majestics.
They fought (though I believe it was Lieferld’s Supreme) to a draw.
If you just want to go on pure feats, Gladiator wins.
Everyone knows that the Saint of Killers wins. From the Wikipedia article: “The Saint of Killers is completely impervious to harm. Bullets bounce off him, a direct hit from a tank doesn’t affect him, being underneath a collapsing mountain simply means digging himself out, and being hit in the chest with a nuclear missile causes no damage to him or his clothes. He can easily knock away tanks with a simple kick and he can be hit by a speeding truck without flinching. He is an expert marksman able to draw his guns at superhuman speeds. He possesses a pair of Walker Colt revolvers fashioned from the Angel of Death’s sword. They possess unlimited ammunition, so they never jam or need to be reloaded. They always hit their mark, even piercing modern tank armor to reach the intended target, and always inflict fatal injuries or death regardless of circumstance or nature of the victim (especially either an angel or demon). Even God and the Devil are not immune to the bullets, considering that the Saint has killed them both”
Saint of Killers is an interesting character, but as a spiritual entity really isn’t a meta-human/meta-alien Superman archetype or variant in any meaningful sense.
Gladiator is only as strong as he thinks he is. Cannonball can, and has, kicked his ass.
Moore’s Supreme is a different sort of beast than Liefeld’s. He’s mythic. Flying through time? He does that on a regular basis. Crossing the universe to meet his girlfriend? Heck, his dog does that.
Heck, Supreme has a whole room in his house (the Time Tower) that does nothing but let him travel through time.
Intergalactic travel is no big deal for him (indeed, one of this foes is a sentient galaxy) and I doubt Gladiator’s ego is going to stand up too long against a being who has access to an entire dimension dedicated to alternate universe versions of himself.
And if any of the other players get sufficiently uppity, they just might find themselves living out the rest of their lives as a photoplasmic light pattern in the prism world of Amalynth!
Is this a fistfight or a fashion contest? 'Cuz if fashion is involved, Vartox loses.
if Fashion is involved, I think Captain Marvel wins in any serious contest. I mean, comon! Double-breasted scarlet tunic? Also, he’s totally sporting that gold waist sash. The lightning bolt says “I’ll fuck you up. Hell, my SISTER will fuck you up!”
All that aside, seeing as Captain Marvel is the alter-ego of a normal kid gifted with superpowers, he’s a superhero that ANY kid can strive to be. 
That said, he pre-dates Superman, so it’s not really fair to call him a knock-off. It’d be like calling The Fantastic Four a rip-off of The Incredibles. 
No, he doesn’t.
Superman: Action Comics #1, June 1938
Captain Marvel: Whiz Comics #2, February 1940
Hm, my bad. Although he still wins in the style department.
Cap’n Billy’s Whiz-Bang does predate Superman, though.
http://www.aboutcomics.com/cbwb.html
Er…not going to be an issue when Gladiator blitzes them all to death. And Supreme has never had combat speed feats on Gladiator’s level.
He’s just too fast.
Man and Superman, though, came out in 1903.
Actually he comes in second. Black Adam’s costume is without equal.