Having also been interested in UFO's for a number of years I think that the number of sightings that could come close to being considered "alien" could be counted on the fingers of one hand - and then probably further research could disprove them.
ones with multiple witnesses (like the Hopkinsville sightings) or photos such as the McMinville photos (sorry about the spelling) could be considered but i can't really think of any others.
I'm quite interested in the ones (such as Rendlesham Forest) which started off as UFO sightinigs but i think hide some much more intriguing mysteries.........