If talking about the worst Star Wars Movie, to me it is The Last Jedi.
If talking about the worst MOVIE of all the Star Wars series (a movie may be great, but be a bad Star Wars Movie. For example, the Last Jedi in my opinion is actually a MUCH BETTER MOVIE than the Force Awakens, but as a 'Star Wars' movie it didn't fill many fan expectations...thus why I feel there is such controversy about it among some groups)....
For me, it's the Phantom Menace. That movie has so many bad movie things about it (from the script to the choice of some of the actors to the stereotyping) that I'd actually put AotC above it any day of the week.
We all have different personal opinions on which movies are good or bad. I have no problem with someone saying AotC is their favorite anymore than if someone said TLJ or even one of the Ewok movies is their favorite. We all have different things that make us tick and our differences is one of the things that make the world interesting.