Answer 1

Actually, Dialga and Palkia Control Space and Time respectively, and arceus is the first pokemon, but mew it's the ancester, it's kinda confusing, also i found this on bulbapedia

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

Answer 2

Arceus created Mew, Dialga, Palkia, and Giratina. Mew created all of the other pokemon, Dialga created and controls time, Palkia created and controls space, Giratina created and controls the reverse world. that is how it works because it makes the most sense and if you have any questions on how i answered this question, e-mail me at dgrittner.atem1@gmail.com

Comments

Just because something makes the most sense doesn't necessarily mean that it's the right answer.

---

Then how did arceus come about?

Answer 3

Think of it this way, the ancestor of all Pokemon need not be a Pokemon itself.. :) So, from that logic, like monkeys are the ancestors of humans, Mew could be the ancestor of Pokemon and Arceus could still be the first Pokemon. :)