Ther have been so many duds, and mostly forgettable, but the ones that really disappoint are the ones that had so much promise, with actors, story or hype...
- Doomsday 2012 (Saw this as new release in the video shop and wasted a dollar)
- Allan Quartermain, Temple of Skulls (Read above)
- Dune - Brilliant books, totally failed to translate
- Hitchhikers Guide (I thought that Donaldson had nothing to do with it and I was bitterly disappointed that he wrote the screen play)
- Johnny English (Mr Bean is bad, this is worse. Rowan Atkinson was absolutely brilliant as Blackadder the Third)
- Return of the Mummy... again... third one anyway.
- Empire Strikes Back? Episode vi. All of the original ones failed at the end anyway, but this one only had the first 10 minutes worth watching.
- Any of the Garfield movies... I mean really, Jon was successful with Liz?? Please!
Must be plenty more, and I will be reminded by others in this thread, but these are the top (bottom?) I can think of.