Origins of Pokemon

[Cshad]

"Although Mew is considered the ancestor of all Pokémon, Arceus is said to be the first of all Pokémon."

Mew is simply the ancestor, Arceus is "God".

What I don't understand is what pokemon is what

What I mean is that Mew is the ancestral pokemon. Arceus is the first Pokemon. So which came first?

Well if Arceus is the fist Pokemon

Then obviously Arceus came first

Also, on that topic, what pokemon created the world? Firt it was Kyogre and Groudon, but then it was apparently the Regi trio. Then the plot thickens as Dialga and Palkia created the world, before it turned out to be Arceus. Anybody understand what is going on?

The universe and space are not the world, so Dialga and Palkia didn't do that at all. Just read the Pokedex entries on bulbapedia. They pretty much say it all.