I think you can argue THX had a cult film status. At least two music videos have been inspired by it. Queen did one in the 80’s and a Hip Hop duo did their own homage in the 90’s.
The angry letters I saw printed in Cinefantastique magazine from readers who didn’t like Star Wars when it came out, wondered how such a film could even be made by the same man who made THX. 😉
Daft Punk referenced THX 1138 as well. 