This was also my first thought.
Iceland rules. Ought to, anyway.
Lord Acton, whoever the heck he was. I don’t recall ever reading a reference to him other than that quote.
And I apologize to Rashak Mani for the tongue-in-cheek dig. But I’m not sorry I picked Brazil, where the futbol fans aren’t content to merely cheer their national team, but bring their bongo drums and bang out their own music from the stands. Now, that’s a nationality that knows how to have fun!
One very petty misgiving I have about choosing a Scandinavian country (or the Netherlands, for that matter) is my concern that, over time, the Winter Olympics would come to supplant the Summer Games in status and importance. That would just be wrong…
[SIZE=1]OTOH, maybe under Greek hegemony the Games would be drastically reformed to capture more of the spirit of the original – you know, ultimate fighting to the death, the marathon being the top event, and everyone competes wearing nothing more than a glistening sheen of olive oil… [SIZE=1] 
John Dalberg-Acton, created Baron Acton in 1869. His famous quote about power and its tendency to corrupt is said to have been made in the context of the 1870 declaration of the dogma of papal infallibility by Pius IX.
Canadian here who could be persuaded of the UK (return to Empire!), NZ or Australia.
Aussie who’d go for New Zealand, Canada or Iceland. They seem like nice people, not too bossy 
Australian, I’m totally with New Zealand on this one.
My biggest issue with the US being a global superpower is the lack of cricket. England or New Zealand would have to be my picks then, with Sri Lanka and India as runners up.
Grand Fenwick.
I’m Canadian and I’d go for New Zealand too. They’re like the country I would sit next to and make jokes with if we had a big assembly. I think New Zealand would get all Canada’s jokes and we would be become best friends.
Invisiblity.
What? Oh. Nevermind.
Well the EU could concievably become the next superpower. That might be ok. They’re more interested in money than war and they’dspend too much time arguing with it other to bother the rest of the world much.
Or Canada. In fact it’s possible they’re a superpower already but they’ve been to polite to mention it.
each other
I’d want a democracy with reasonably good track record in human rights, and no nasty habits of starting wars in recent history. US is out (that war thing), and I’m afraid Brazil doesn’t make it from a human rights point of view. I really would prefer something that isn’t in Europe (not that I have anything against Europeans, some of my best friends are Europeans (all, come to think of it), but our track record in world domination isn’t the best…) Frankly I think EU would be a shitty superpower – if I had to choose between that or USA it would be one of those plague-or-cholera dilemmas.
Maybe South Africa. How well functioning is their democracy these days?
I’d pick Sweden or Norway. They have a system that seems to work rather admirably.
My vote goes to Australia.
They’re already arrogant, loudmouthed and boorish enough* that the lust of power wouldn’t be likely to corrupt them, and in my experience they hardly ever go around invading anyone else’s country.
(* Only kidding, cobber. Honest. )
That’s 'cos we don’t give a rats arse about anything.
Talk about an apathetic superpower.
Of course, if Oz ended up a superpower, y’all would need to adopt g’day as a greeting which would just drive us nuts and we’d blow you up for lack of being able to pronounce it propl’y.
I’d suggest NZ, but their accent would drive countries to madness
Ummm. Antarctica get’s my vote. Huh, what ?
Seriously, I don’t think Australia would be that good at the job. We can be a bunch of self-righteous pillocks. We can do a lot of good stuff mind, but so can the USA, and if we became a superpower, we’d also make the same mistakes they have, and in fact, we’d not be much different at all.
The more I think about this, the more Thailand seems to be my preference. You can piss a Thai off, you can make him violent, but it’s not easy, and for the most part, they’d just let the other countries be, and providing we all have enough chilli in our diets and we smile a lot and are polite to old people, they’d not send the tanks in.
New Zealand would indeed be a fine pick. Folks are just too kind to nuke you.
The EU would also be good. Very mature, weather-worn, and world-weary superpower that would be. Too jaded to nuke you.
But really, it should be Jamaica. Too stoned to nuke you.
Given the choice of the some of the bigger powers (or future powers) EU, China, Russia, India and the USA, I think I prefer the US.
The United States.
The EU is a nightmare enough already without granting it extra, albeit hypothetical, powers 