A lot of these cross over ideas are cool but let's face it, we all really want
MK vs. SF and DC vs. Marvel
Instead we got the opposite so far lol.
On the DC vs. Marvel front, both have powerful cosmic beings.
Marvel has a lot more popular cosmic characters(like everyone milks Galactus and Thanos), but not necessary more powerful than DC's. Example, Marvel's known for Living Tribunal, Beyonder, Frank Richards, Shuma, Celestials, Eternity, SS, Galactus and Thanos. Not counting TOAA(God of Marvel)
DC on the other hand has just as much if not more but ultimately more powerful...The Spectre(apart of God essentially), Imperiex, Anti-Monitor, Superman Prime One Million, Cosmic Armor Superman aka Thought Robot, Ion(Kyle Rayner), White Lantern Kyle Rayner, Oracle, Mxy(this guy could arguably solo any universe world's funniest), GEB, Phantom Stranger, Jenny Quantum, Dr. Fate, Lotus, Darkseid, Brainiac, Doomsday(eventually became a cosmic threat adapting to literally everything)Hellspont, Dr. Manhattan(though not apart of the mainstream DCU still DC character) Not counting(The Presence/God of DCU)
At the end of the day, DC>>>>Marvel in terms of raw cosmic and multiverse/universal power.
Some of these guys would be too much for DBZ but some could be more even for sure.
There are CERTAIN crossover DC vs. Marvel match ups that would have happened like Superman>>>>Hulk. No doubt. Flash>>>>>QS, again no doubt. SS>>>>GL(normal Kyle would lose, Ion would erase SS however) Storm would in no way beat Wonder Woman. Lobo would not lose to Wolverine, Darkseid would most likely lose to Galactus however Darkseid I believe would beat Thanos(thanos does his crazy feats with power gimmicks IG, HOTU, gems etc) normal match I'm pretty sure Darkseid would murk him.
The Superman vs. Thor debate I know is a life long heated debate, however honestly at the end of the day Superman would more than likely prevail. Simply stronger, faster(much faster) and has more abilities to work with. Thor while has magic and mjolnir etc is a one trick pony, he can't do much without the hammer and even The Hulk has punked Thor a few times including taking his hammer or breaking it...yet Superman KOed Hulk pretty easily in the crossover so...yeah. Plus, Supes honestly has beaten more powerful magic beings Darkseid, Imperiex etc over time to name a few offhand. People who would arguably one shot Thor if Hulk has beaten him...