Like The X Files, Project UFO dealt with sightings of alleged interstellar travelers. That, however, is where the similarity ends. While X Files was pure sci-fi, and heavy on emotion, Project UFO was actually fact based, if somewhat loosely. The episodes were taken from the files of Operation Blue Book, the Air Force investigations of strange sightings in the sky. This was stopped in, I think, 1968.
As in real life, most of the sightings in the episodes were explained as earthly phenomena. But not all. I haven't seen it since it's original NBC run in the late '70s, but I do remember one episode that ended with a strange intelligent creature communicating with a little boy, explaining the creatures journey to Earth and telling the boy not to be frightened.
It was produced by Jack Webb's Mark VII Productions, adding an extra air of credibility, something The X Files lacked. I don't recall if it has aired since its original run, but it should. I think Sci-Fi could find room for it, and I believe there would be an audience for it, even though it was relatively short lived. A complete series DVD set might find a market too.