I've gone to movie theaters alone - but re nimh's question, I don't think I've ever been the only one in the theater. I do remember being, say, two of us with four or five others. The old FoxVenice, in, natch, Venice, showed two movies a day, every day for years, changing them all the time. Sometimes the audience was spare, which was too bad for the theater revenue (and it eventually folded) but pleasant for the rest of us. We tended, for a while, to see six movies a week.
On the other hand, I liked being in that theater when some oldie or somewhat exotic to us films were shown, and a large audience as a whole really got into the movie. So many good films, so little time. The audience wasn't usually loud, this was in the seventies, but you could apprehend total attention happening. Well, we were loud with the San Francisco Mime Troup, but that was theater.