Apocalypse never does what his comic book writers allege he can do...I mean, between the mass-energy and shapeshifting alone he should be pretty much unstoppable. Of course, Magneto should be able to control all matter since observable material properties are pretty much 100% caused by electro-magnetic phenomena, but that's how comic logic goes.
Gladiator's powers are vast, but vary almost randomly every time we see him with no clear explanation as to 'why'. His powers are also specific, he can do certain things very well but doesn't possess the arbitrary expansiveness that Apocalypse does.
So, unless Gladiator can outright kill Apocalypse by brute force, a well-written Apocalypse wins through versatility and near omnipotence.