The United States is the only super power at this point in history. Whilst Europe may have a huge economy remember that its still a collection of lots of nations and some of them (notably club med) are weighing the union down with their eccessive debt (and plenty of people are now dumping the Euro in the short term because of this). Plus outside of the UK and France Europe doesn't reall have the military might to be considered a superpower (and those countries don't have enough power alone or collectively to be super powers).
In my mind you need both the economy and the military to qualify as a superpower. China may be growing rapidly but they cannot project their power around the world yet. So they don't qualify either.
Neither does India.
I'm not sure about Russias projection capabilities, but I know The United Kingdom has significant projection capacity but nowhere near whats required to be called a Super Power.
In the future however, China will become a superpower. They're already developing significant amounts of countermeasures to US dominance in their part of the ocean to deny and slow US access. If a war broke out tomorrow the US would prevail however. Of note is that even when China becomes ecenomically larger then the US it will still probably take a long time after that before it can overtake them militarily I think.
What China also lacks in comparison to the US and the UK is cultural power outside of its borders. The US and UK are huge cultural exporters that dominate the world with their culture, this is aided by the fact that both countries are democracies and thus get along very well with the other democracies in the rest of the world. Which is something that China will always lack in its current form. I think the US can probably rally more support amoung the most powerful countries in the world more easily because of that simply fact.
