Are there any actual gods in Marvel comics?

There are many beings that have very big powers. There are beings that are worshipped as gods (Asgardians; and I would lump Azazel into that as well since Marvel seems to imply that he's - while a mutant - someone people consider to be "Devil"). There are mutants whose power would clearly have been considered as "god like" by people worshipping Greek or other polytheistic pantheons where the threshold to what made you a god was pretty low.

But are there any actual major "Gods" in Marvel universe?

Since there are many different definition of what a "god" is, the one that is pertinent to this question:

1. 
   

   Power wise, being able to create Universe(s); e.g. gods more in a sense of Christianity/Judaism scale rather than "Pan" or "Hestia" in Greek pantheon who merely have some limited supernatural powers over small domain of natural events.

   
   


2. 
   
   

   Effectively immortal, at least excluding specific exotic attacks.

   
   


3. 
   

   Origin-wise, be "supernatural", not merely a human mutant or a powerful alien with advanced technology.

   
   


4. 
   

   Desire/demand/like followers' worship or prayers.

   
   

Answer

One-Above-All

There are many "gods" in the Marvel Uni/Multi/Omniverse, but presumably the most powerful is the One-Above-All, a mysterious entity said to be the "creator god" of Marvel, and has once been implied to be Jack Kirby, the then-partner of Stan Lee and co-creator of many characters, who was represented in a Fantastic Four comic (issue #511) as a god-like entity who took the form of a "comic book artist" looking very similar to Kirby (though this is probably unlikely).

This picture comes from the Marvel Wikia.

Elder Gods

Next, there are the Elder Gods, listed as the "first kind of gods" who were created by the Demiurge, another cosmic entity living as the sentient force of Earth's biosphere.

An image from Comic Vine:

New Gods

The New Gods are immortal, human-like beings that are not as powerful as the Elder Gods. Known New Gods are worshipped by Earthlings. The likes of Odin and Zeus, among others, have sometimes been referred to as "new" gods, but whether or not they are is debatable.

Celestials

Maybe not "gods", the Celestials were born at the birth of the universe, and created life, death, and apparently the multiverse itself. However, they restricted all interactions with humanity long ago, and thus humanity has all but forgotten them.

The leader of the Celestials is called the One Above All (without hyphens) and, like the rest of the Celestials, he may or may not be an actual god. However, he is not to be confused with the One-Above-All, the actual creator god listed above.

Some Celestials:

Gods by Race

In the Marvel Universe, many different races of humans and other species worship many different entities, classifying them as "gods". This list can be seen here. This includes Norse Gods, such as Thor and Loki, and Skrull Gods, such as Kly'bn and Sl'gur't.

Examples:

• Storm, the weather-based member of the X-Men, is worshipped as a goddess in Kenya.


• Beta Ray Bill, a being with Thor's powers, is worshipped as a Norse God in some places, but is by no means a Norse God.



• Selene, the "Black Queen", is worshipped as a goddess in Marvel's Nova Roma.


• Demons, former Elder Gods, are still worshipped as gods by some.

Conclusion

There is more than one "god" (millions, in fact), as classified by your standards; however, there is only One above all.

Think of it like this (if you are a Tolkien fan): One Above All is to Marvel as Eru Iluvatar is to Middle-earth.