If Nintendo released a HUGE, well-done, polished and serious Pokémon MMO and updated it and held tournaments and so on - and it had a monthly fee - do you think it could have become as huge as WoW is?

It would be larger, especially in Japan.  But it will never happen.

Maybe before WoW had not come out. Right now, no.

I don't think it would be larger then wow, wow is simply too established, but the ingredients are certainly there for an excellent and very sucessful MMO.

I'd imagine Whoever developed it would need to have some experience with creating MMO's though, and a very large and creative team to continue to support it.

Nope.
Maybe it would attract many players at the start, but keep them playing for 4+ years without them getting bored ?
Seriously doubt it...

The problem with this is that WoW appeals to a much, much larger age group than Pokemon ever could--Nintendo would get tons of pre-teens but that'd be the limits of their audience. (And that audience would, in turn, be limited by their parents who would be footing that monthly bill.)

Even then, I think it'd be a terrible idea for Nintendo from a pure business standpoint.

How much has WOW sold again? Pokemon could mabye do ten to twenty million people playing, is that enough to beat WOW?

The biggest problem is that a big part of the pokemon fanbase are kids. And their parents won't allow them to spend a monthly fee for a game which is addicting.

WoW is 12 million strong.

hell no!