Obviously some people count the fact that Johto and Kanto share a landmass as a negative, because in some ways it does detract from Johto (like Yamato-san said, the game designers totally screwed up the gym leaders' levels, no question) but seriously, I like the fact they share a landmass. It gives Kanto and Johto a unique situation; as opposed to just having independent region after independent region (which, let's face it, could get kind of boring), there are all kinds of plausible political or law enforcement issues that could arise from things like having to share Elites (who has seniority?) and border control (all those poachers passing from one to the other!) and so on. ^.^;;
what would be the point of border control? In case you're unaware, most of what we've seen of the Pokemon world so far is all one country (this is why they use the name "National Dex"). Japan, the actual country it was based off of, is also composed of several regions (and the Pokemon world "regions" are each based off of a region in Japan, likewise).
Well, I think the individual author should decide; there shouldn't be a "be all end all" rule for something like that, mainly because everyone depicts religion and the legendary order differently in fics.
Personally, I've taken to saying "oh, dear Mew" even over MSN, and despite what the games so I will NOT sacrifice Mew's name for that of Arceus, who doesn't impress me. When he contains the DNA of every single Pokémon and becomes all cute and fluffy, maybe I'll change my tune.
But anyway. I don't have a clear-cut decision on this, and probably never will since I just don't know what to make of Arceus. In general, though, I like making up other expressions to replace the term "god," such as "By Lugia's wing!" or "Rayquaza's tail!" just to show that it's not just one legendary that has an expression named after them. I think that all of the legendaries are considered to be gods to an extent, but I've never really focused much on religion in any of my fics, so meh. According to canon, Ho-Oh was worshiped back when the Tin Towers still stood, so I'm sure that there's a cult for it at the very least. *sees a plotbunny sneaking up on her but ignores it before it can jump into her head* Otherwise I have no real ideas and just sort of assume that there are plenty of religions, though.
I've heard that the majority of Japan is inherently atheist. Now, you could argue that Shintoism and Buddhism are religions, but the majority of Japan just seems to have adapted their spiritual beliefs as opposed to heavily following their creation myths (and unlike other religions, I don't believe they've tried predicting any sort of apocalypse). In the case of Shintoism, it's said that a near-infinite number of gods exist (among them are deities representing everyday objects). As a result, followers are tolerant of other religions and even adapt the gods those religions believe in as their own (it's worth noting that they have Christian ceremonies, most notably western-style weddings).
Of course, these "gods" aren't seen as omnipotent, but more as high, spiritual beings that're in-tune with nature. I imagine this is how the legendary Pokemon were meant to be portrayed (this portrayal seems particularly prominent with the earlier legendaries.... they didn't create the world or move continents, but just higher beings with power over the elements of ice, flames, and lightning. On top of that, the second movie had shrines dedicated to these gods, just as there're several shrines for the numerous Shinto deities). Even if they are creators, like Arceus, what power do they have now once the universe was created? They can't supposedly control fate and exist everywhere at once, like how the Christian God seems to be portrayed. It'd be like a parent being able to manipulate the free will of their own child, it just can't be done, and it's why Arceus has a seemingly immortal lifespan, yet isn't completely invincible in battle just like any other existing Pokemon (for that matter, they might not even be capable of stopping what it is they started, so I doubt Arceus can destroy the universe in spite of creating it).
In this sense, Shinto gods act a lot like they did in Greek mythology (I heard a good argument that the 4th generation legendaries seem to be based off of Greek myths, actually). Maybe, much like how Shintoism adapted the gods of other religions, there is no evidence that these Pokemon gods even created the universe, time, space, anything, but are only believed to have done so by particular believers (given, there's no doubt that Pokemon like Dialga and Palkia are capable of rending these elements, but actually creating, or even controlling them, is another issue). I'm not sure, but I think Shintoism may've also adapted the idea of the Christian God, because quite often anime characters (even those who don't appear to be Christian) can be found praying to "Kami-sama" (God). Not any particular God, just "God", which probably emphasizes the idea of a formless omnipotent being, possibly the manifestation of the universe itself. If such is the case, then the idea of any creator deities which possess a physical form of any kind being the highest thing in existence would be made completely null and void.
As for the whole question about replacing 'god' with 'Arceus': no, I do not do that. This is for a number of reasons, one being my aforementioned attempts to take some emphasis away from Pokemon in my canon. It is, believe it or not, possible to use real animals alongside Pokemon (I used regular bugs in my script), so the idea of using real world religions, with the actual deities they believe in, doesn't seem impossible neither. I find the idea of replacing a Pokemon's name in an everyday expression cheesy as hell anyway (that isn't to say new expressions could be made up with Pokemon, maybe have a character go with an "It's like they say..." sorta thing, but I don't see an expression having any relevance to the stories I have planned out anyway).... lastly, there's the fact that I want to write my story in Japanese, and a lot of the idioms and such which this question concerns are mainly English expressions (but that doesn't mean I can't still have characters pray to "Kami-sama" or shout 「オーマイガッ！！！」 "Oh my god!!!" using gratuitous English in the Japanese version). But even if I adapted expressions in the English "translation" (if you could call it that ^^'), I still wouldn't try to insert Pokemon into them.
XD Well, I don't personally imagine Christianity to exist in the pokémon world, and even if it did I wouldn't include people singing songs in my fic. But meh, different strokes for different blokes. ^^;
aside from all the stuff I said earlier, Christianity actually has been shown to exist in Pokemon canon. You fight a Ghost-type Gym Leader in what appears to be a church in Diamond/Pearl, and a certain
anime episode quite clearly invoked several Christian themes.
