In 2004, Lucas released his Director's Cut of THX 1138. There are no changes as big as making Greedo shooting at Han, but the there were still some controversial changes. Here a quote from The O.C. Wikia George Lucas article, Controversy section.
Changes Lucas personally made to THX 1138 for its 2004 DVD release further re-enforced criticism from fans who felt that he was spoiling the integrity of his original films.
As an example, a significant change he made with THX that he didn't do to Star Wars was reordering some scenes. You could see a exhaustive list of changes here and here. Here is the whole Postscript section of the first link (Emphasis mine):
Although the story stays pretty much the same the movie has been extensively changed. I'm sure George Lucas would claim that he couldn't accomplish his original vision back in 1970 due to the technology of the time and budget, so changes and additions could be seen as reasonable. The thing is though, George Lucas doesn't mention on the DVD that there has been any changes made at all, in the interviews, commentary, packaging, anywhere, the only mention is that the movie has been restored, this all seems very strange indeed...
As you can see George Lucas and ILM have done a wonderful job (except for the ones I have mentioned) in updating and widening the scope of THX's world for the masses to enjoy. This is a testament to the original movie that it can still be viewed today without looking too 70s. Some people may not like the changes, preferring instead the original, however, in my opinion they are both excellent. The George Lucas Director's Cut should have been released with the restored original theatrical cut rather than the way it has been released.