Whether aliens are real or not is a matter of personal opinion. Currently, there is no proof that there exists 'intelligent' life on other celestial objects, but there is no proof that there isn't. See www.universetoday.com/74513/are-aliens-real/ for details.
yes, as a matter of fact there is a bug that can live in earth and in deep space :) also I don't think we have the whole universe just for the humans. there should be more out there but we haven't met yet
We may be aliens to earth: scientists have speculated that life may have begun elsewhere in the cosmos and had been carried to earth, possibly by a meteor. This is one of the mission objectives for evidence of ancient life form developments by the current Curiosity Rover currently exploring Mars.