We all know what arguing on the Internet is like, but none of us can stay away when someone is wrong. Here are a few opinions I hold which often provoke a response in sf forums:
1. Paul Verhoeven's Starship Troopers is an excellent film, but the novel on which it was based - by Robert Heinlein - is right-wing rubbish.
2. The sequels to Frank Herbert's Dune do not decline in quality. In fact, the sequels are better-written books than Dune. (Until, that is, you get to the ones written by Brian Herbert and Kevin J Anderson, which are appalling.)
3. The Wrath Of Khan is not the best Star Trek film. Its sequel, The Search For Spock, is a much better film.