Idk if I believe that UFOs are aliens but I believe there are other lifeforms out there, possibly more intelligent because they've been around longer or some other reasoning. I'm not a die-hard believer but I prefer this belief over the "aliens don't exist" line of thinking because of the creative aspect that goes along with it (tv shows about abductions, short stories about interplanetary visitors, art based on alien planet landscapes). It's more entertaining to believe, I think.
Also, if anyone's interested, here's a video of Dan Aykroyd discussing his encounters with possible alien lifeforms. It's a bit long but interesting if you like UFOs and the like.