Master and Commander, and Saving Private Ryan on a list of worst movies ever? I would put those as among the best ever. Although Saving Private Ryan loses points from me for it's "Hollywood" ending, Band of Brothers is waaaaay better.
I've been trying to think of what is probably the worst movie I ever saw, and it's hard as I try to avoid bad movies. However, I, and some friends of mine, from time to time have a "shitty movie night" where we watch a truly fuck awful movie for fun. Someone has already mentioned Surf Nazis Must Die. But I think I got that beat with Deadly Prey (1987). An incredibly lame knock off of 80's action movies like Rambo and Commando, but like Paul Verhoeven's Showgirls it's so bad it's good. They even made a sequel in 2013 called Deadliest Prey, I haven't seen i yet, but it is apparently just as awesomely bad as the original.
Then there was when i was in my mid to late teens, my girlfriend, at the time, and her friends had a goal to watch every movie that contained underage frontal teenage male or female nudity. Turns out there are a lot of such films, mostly European or South American and from the 70's, 80's and early 90's. So I had to sit through some truly awful movies just because they had a scene where a 12 to 17 year old boy or girl shows frontal nudity for a second or two. Some of the movies could be considered child porn today, some of them actually were child porn back in their day. I don't remember most of them, but one I remember being forced to watch when I was 15 was Genesis Children (1972). A terrible, terrible "movie" if it can even be considered one. It had almost no plot, the acting was totally amateur and the only purpose of the movie was to show naked teen and preteen boys running and frolicking on the beach and in the water, often in slow motion with graphic close ups of their flopping cocks and bouncing balls. When I voiced my criticisms of it, the girls I was watching it with accused me of being homophobic. But yeah, defiantly worst movie I ever saw was Genesis Children.