Although the singled out Versus is pretty silly, and the X-Men are far too old for the older, but less powered up since their youth Titans, I'll bite anyway...
Roy harper vs Cable -- Cable has just as good aim and he's got guns
Wondergirl vs Rogue -- Rogue is stronger, and has other powers
Beast boy vs Collosus -- Colossus cannot be hurt by Beast Boy
Raven vs Marvel girl -- Marvel Girl is Phoenix. Nuff Said.
Starfire vs Emma frost -- Emma Frost is a viscious telepath.
Wolverine vs Dick grayson -- Batman can handle Wolverine. Nightwing Cannot.
Cyborg vs Bishop -- Bishop absorbs all.
Tim Drake vs Gambit -- Tim Drake is great, but Gambit's faster and more destructive
Superboy vs Warpath -- Superboy dismantles Warpath, too many powers.
Kid Flash vs Nightcrawler -- Too much speed involved, it could go either way in a heartbeat
Aqualad vs Storm -- Storm is on the planetary scale...
Terra vs Polaris -- Polaris is on the city-wide scale
Redstar vs Cannonball -- Cannonball is immortal
Hawk vs Beast -- Beast crushes cars with his bare hands
Dove vs Arch Angel -- Angel fears nothing.