Let's look at what they are first.
An Alien is defined as a life form not from Earth. Also known as extraterrestrial life.
First off, I'm not sure that I believe in UFOs and aliens. There could be something else out there in the galaxy and beyond since Earth is a small part of the universe, etc., but I highly doubt anything would really go all Independence Day or Men in Black on us. Who says they'd be the little green men movies portray anyways? I enjoyed the Alien and Predator movies, especially Alien vs Predator, but for me that's just entertainment. There's an episode of the TV show Supernatural that I loved where there were supposed alien abductions, but the real cause of those "abductions" was the Trickster.
Although, if people believe in aliens and UFOs, great. I've been in Arizona and seen pictures of strange lights. I've seen some myself, but a lot of the alien lights could very well be military aircrafts. They've got some pretty fancy stuff.
That being said, I'm looking forward to seeing Cowboys and Aliens. *grins*
What are your thoughts on UFOs and aliens? Have you seen Cowboys and Aliens yet? What did you think?