Yes. With all the millions of planets out there, chances are there must be at least one other one capable of supporting life.
However, I don't believe in aliens in the form of little green men or anything like you see in the movies. I don't believe they have UFOs or anything ridiculous like that. If they could fly to find us, we would have flown to find them by now. And, all this crop circle stuff - why would they come all the way here, to leave some marks in the ground and leave again? I'm pretty sure they would have stayed and explored, or at least stayed long enough for someone to get some proper reliable pictures/footage and it would be all over the news. I just don't believe any form of spaceship could come here without it being noticed by thousands or even millions of people. Just my opinion.
When I say aliens I mean any type of life form, most likely bugs etc