Robocop 3 didn't suck as much as Robocop 2.
As for Manos, I don't think it belongs on that list. Manos was made with the budget and techinical restriction (why is every shot only 18 seconds long? All they had to film with was bits of film that were 18 seconds long) and while it is a doozy of a loser, the only reason it's there is because it's the worst movie to ever appear on MST3K. Yet I don't see Monster-A-Go-Go which is definitely much more boring.
But I could go on and on. The good thing about this list is a lot of movies they put on were just plain BORING. That's the only real crime for a movie to have: to be horrible when played straight and too horrible to mock. Other than that, I can't think of any movies on there I'd be obliged to save.