I own Terminator, as well as two and three. I’ve watched a couple of others, but found I lost track of how many there even are. It might as well be a TV show at this point. I got that way with Transformers and Avengers as well.
As an aside, I think it amusing that OJ Simpson had been considered for the role of Terminator in T1, but James Cameron dismissed the idea saying that Simpson would not make a convincing killer.