Why isn't Thor or Asgard the real God and Heaven?

I never got why Marvel thinks Thor is balanced enough to fight with the Avengers when he transcends Marvel's U's metaphysics tremendously, or at least the highest science. Thor is a God, God's are beings of divine and omnipotent might and incorperal power. No universal theory can define them, yet Thor as he is can be mistaken known as any top tier class of mutant or alien due to his size and medival garbs he wears instead of a divine being. I always wonder why such a magical lifeform that operates just like an Angel instead of a cosmic or top tier alien co exists with the apparent onimpotent all knowing god almighty when he can be defined as such as well. Odin as well. Asguard in it's definition is called the realm eternal, and it has a paradise called Valhalla, why isn't called the real heaven too?

Thor should be a being that brings miracles and blessings like a messenger of God, but he sticks around arm wrestling Hulk and following a mere mortal who is like God in attitude. This confuses me, a god who fights off galatus and tanks universe wiping bombs and he's not the real god?

Because historically Gods were not omnipotent until the advent of monotheism. They were just powerful beings that each controlled different aspects of life. What you are calling gods above in the Marvel Universe would be beings such as The Living Tribunal and Pre-Retcon Beyonder.

Like Lateralus said historically most gods were not all-powerful beings. They were usually far more powerful than regular humans, but not omnipotent.

Also, the Asgardians are not the only gods in Marvel. Virtually all other pantheons have been shown to be true. So all their afterlives are real. Its impossible to say one is the "real heaven" when all of them are real heavens.

All in all, your post comes off more as viewing the whole deal strictly through the lens of monotheism without considering the differences in polytheism.

Whereas gods of the Marvel U still maintain a unique identity in the books, having distinct qualities and features, they are not omniscient beings. Plus, there are a bunch of other pantheons in Marvel. Far less explored, but still there.

If you think about it all the major Gods live in Marvel so he cant come to Earth and claim the divine rights

both are evidently myths

Well there's the one above all still and the actual Christian God I'm pretty sure in the marvel universe. And Thor still gets respect as a god. People pray to him and he answers prayers. That's pretty godly.

Just for the record, there is currently no evidence that the Christian God is The One Above All. Given how every other religion both alien and Earth are the same type of god and the one Ghost Rider story to heavily deal with Christanity did not portray God or the angels as any higher than the others for now all evidence points to the Monothestic God being another skyfather.