Okay so of course to answer this some people should first probably know how big the Pokémon Multiverse is (since obviously some people and especially Pokémon downplayers probably doesn't know anything about how big the Pokémon multiverse is) so for starters :
The pokemon multiverse is an infinite Multiversal cosmology , which has a metafictional detail which says that game sold is a different "universe". In addition, every game has countless universes by the ultraumbrals, and some others paralell dimensions. This will be explained below :
About The Metafictional Detail
Well, so many people says that the metafictional detail is just wank, but, nevertheless, this is backed by multiples NPCs and texts in game.
Pokemon Black and White
In this games, there are probably the most important feats regarding this `metafictional detail´: the Entralink.
What´s the entralink? The entralink is a place where you can travel to the world/universe of another game, as you can see here.
"This is an island called the Entralink. It´s located in the center of the Unova region. The entralink is a mysterious place where you can connect with someone´s world"
A synonimous of world is universe, even if we don´t take this into account, the `world´ of that "someone" is another created created by arceus, with its legendarys and the same cosmology as the `original´ (since, after all, it is also another pokemon game, isn´t it?). This place appears in the manga too:
In ROZA, there are some other feats about this metafictional detail. First: The Game Link Cable.
The Link Cable is thought to be what was going to be used to send the meteor to the alternate Hoenn. The Devon Corporation was also already working on one, meaning that Link Cables are canon as a concept to Pokemon.
Here, you can see that the pokemon travell across space and time to reach `you´
GameGuides obtained a Time Travel Award for his base.
In pokemon SM/USUM, we obtained another feat about the metafictional detail: the Festival Plaza.
But, why do I mention this? Just see that
"This is a secret place where you can come to play using communication features. We´re holding a festival where trainers can interact right now"
That confirm too about the metafictional detail... but, isn´t that a game mechanic? Well, if you played the USUM´s postgame, you saw that. In the postgame, the Team Rocket interact with the festival place.
Yes, every game sold is a different 'universe'. But... what does this imply?
Pokemon has 340 million units solds as March 2019 and more than 6 millions pokemon SwSh sold on 21, November, 2019. This implies a minimum of 346+ millions universes for pokemon. A high level in the Multiverse cosmology , but, that´s not all
In addition to the main dimension in every game there are other dimensions such us:
It implies a world where the ultimate weapon was never even built, a world where the Mega Evolution is unknown: a different world, in other words.
Another worlds where the villians fulfilled their duties (that can be include inside the Ultra wormholes worlds)
At least 13 other worlds (probably there is probably more, in that case, it would be an inaccurate amount)
Dialga talks about the future world as a 'new world' (even when he has the control of 'this world' in a bygone era'), as 'the world from darkness'.
He uses 'world' and 'planet' as different concepts (world = universe; planet = The Earth)
That´s so easy, as you can see here, there are countless warp holes to different worlds. This worlds should be as big as the original world (as we can see in the reverse world and in the guzzlord ultra ruin world (if you speaks and read the dialogues of the different objects, you can check that this world is a post apocalyptic world, this scene happens in Hauoli City)
The Pokémon Multiverse has at the very least countless amount of universes at bare minimum
•Dialga, he created the time (and is omnipresent in the time) in all this universes. Also he distort the timeand bring the destruction of all things. He can doan attackAble to destroy all the world with palkia
•Palkia, he created the space (and is omnipresent in the space) in all universes. Also can distort the spaceand bring the destruction of all things. He can doan attackAble to destroy all the world with Dialga
There is the fact that Pilikia ans Dialga were destroying the entire space-time contenum and Arceus scale above them all :http://imgur.com/33vTfc6
Those are clear cut multiversal feats and there is even more :
So this Clearly proves that Arceus is Multiversal and Omnipresent across all space and time due to him embodying the entire multiverse there is also the fact that Arceus true form is basically the Whole Pokémon multiverse but I'm going to explain this later I'm just gonna give you an idea about why they embody the entire world (the Pokémon verse) :
There are much more evidence but this should be enough but anyway the conclusion is that Arceus, Pilikia, Dialga are only avatars (and this includes Arceus from the movie and manga and game) and theire true forms embody the whole Pokémon world so killing theire avatars is useless if it doesn't affect theire true form
Debunking the Meteor feat
1) as shown above Arceus multiversal feats are clear as a day bringing a single PIS feat and some game mechanics from the games to downplay Arceus isn't an argument
2)on top of that many people take the Meteor feat out of context, the reason why Arceus died was because the Meteor explosion removed all of Arceus life plates which made him very weak and then he lost his consciousness because of that, so he didn't die because the Meteor itself
3)like I explained even if we assume that Arceus got killed by the Metor this would scale only to Arceus avatar and not his true form who embody the whole Pokémon verse to the point that he exists across all space and time due to his big size