Is it possible that all religions are worshipping the same god?

Yes of course all are worshipping the same "god", although the word god carries some baggage with it. Surprising no one has yet mentioned Buddhism, many assume that Buddhism is pesimistic at its core claiming that life is suffering and all that. Nirvana, or that mysterious place were you cease to exist yet exist all around can be perceived as god mainly because you have been unified with the energy that forged this entire reality. At the heart of Buddhist creation epics is a phenomenon which parallels current scientific understanding, namely that the birth of "god" or energy/light whatever you want to call it was the result of white light finally attaining enough energy to explode into existense. The energy or catalyst for this necessary explosion of a dream like existence is Nirvana/God/supreme being/ultimate truth.

This world never have coalesced into one form out of such diverse and antagonistic parts if there wasn't one to unify such diversity. Their very diversity would break apart the unity imposed upon the world. Such an order would not be able to maintain along its path so fixed in time, place, location, season, and change if there was not one stable and sovereign power. Whatever this power is, which keeps creation in motion and stability, I use the word everyone uses, namely God

-Consolation of Philosophy