If you know more about pokemon than the average gamer, then you should know the confusion of the creation of the pokemon universe.

Here is the confusion:
(Description of Mew in D/P/Pt) Because it can use all kinds of moves, many scientists believe MEW to be the ancestor of Pokemon.
-Which would mean Mew is the creator of all pokemon

On the other hand, Arceus:
(Diamond description) It is described in mythology as the Pokemon that shaped the universe with its 1,000 arms
(Pearl) It is told in mythology that this Pokemon was born before the universe even exsisted.
(Platinum) It is said to have emerged from an egg where there was nothing, then shaped the world.

(points to platinum description)
If that were true, that means Arceus created everything, but Mew created all the pokemon (which would include Arceus) which would mean Mew was created before the universe was even created by Arceus so Mew wouldn't be there to create Arceus... (and a paradox occurs).

So what truly happened? Did Mew create Arceus or did Arceus create Mew?

EDIT: so after much thought, here is what most people think...
Arceus created the universe, Mew, Dialga, Palkia, and the lake trio,
Mew created all the other pokemon
Dialga created space
Palkia created time
and the lake trio made the emotions and the stuff about man kind.

Close enough?

I've always thought Arceus created Palkia, Dialga, the lake trio... But also another sole Pokémon, Mew. Then I believe Mew inherited enough of Arceus' DNA to be likened to Arceus, Dialga, Palkia and the lake trio. And then Mew created all Pokémon while the other deities created humanity.

Arceus created Mew.

Why would a god be created by a weaker pokemon?

Of course Arceus created mew.

My theory is very simple but logical, and it comes from a good and specified Chemistry lesson related to the Big Bang.
Anyway, the theory is that Arceus came out from an egg which came from nowhere as I think till now. After that, Arceus created Dialga, Palkia and Giratina. Dialga created time and Palkia created space. In chemistry, by combining space and time, matter is formed, but to form the universe, you need the inverse; antimatter. This is the role of Giratina; to create antimatter. With the matter of Dialga and Palkia, and the antimatter of Giratina combined together, the Big Bang will of course occur and the universe will be created.
With the universe created, Arceus created Mew which formed all the kinds of Pokemon, except for Mewwo and the other legendary Pokemon who were created by either humans or Arceus. Nevertheless, these living things needed some emotions, thus, the trio was created. Another use of them is the maintain of the titanic dragons.
Hope I cleared!