If you want to get into the worst films with a higher budget and higher expectations, I nominate these two:

DisASSter Movie. I shut that shit off after 5 minutes, it was that bad.

"Frozen" was the first one to come to my mind. Meaning not the disney movie but that one where they are skiing and then wolfs appear and so on.

Re-Animator springs to mind for me. I heard it was a cult classic and found it on Netflix. My wife doesn't watch horror movies, so I saved it for a time that I had to myself. It was so bad. Just terrible acting. And the ending. Just no words for it.

Someone above mentioned Year One. I will second that. I didn't even make it through that movie.

Bad Movies I Actually Enjoy

The Room
Reefer Madness
Showgirls

God's Not Dead

Just Bad Movies

Date Movie
Any Scary Movie after 1 I had the misfortune of seeing.
The Fighting Temptations
Expelled: No Intelligence Allowed
Exodus Decoded

The worst movie I ever watched was probably "I Spit in Your Grave". I thought it were a decent horror movie, but it's just one hour and a half of torture. It's gross. Disgusting.

Also, the sequel is a copy/paste of the first movie (Even the ending is the same), so it's not much better either.

I forgot about this one: 1993's Carnosaur, came out just a few months before Jurassic Park

Romeo + Juliet (1996) is certainly up there. It's the only time that I ever walked out of a movie theatre in the middle of a movie. My girl and I hated it.

I saw something much worse last year. But, it was so bad I've forgotten the name.

The boy who could fly

I had a similar experience with Re-Animator waaaaay back. 1993. The Golden Age of Rock. After hearing good things about it I gave it a rent with a friend. We did not make it to the end.