Generally when I'm watching a movie that sucks, I like to think what I might have done to save the film from total suckery had I been the studio head. (In a perfect world, I'd be a studio head, and not the soulless automatons that produce crap like "Knight and Day"). Here's just a few films that I would have improved:
1) Jerry Maguire--have Renee Zellweger's character get caught in a love triangle between Jerry and serial killer Aileen Wuornos. The seminal point in the movie would be where she bashes Aileen over the head with a fish tank, screaming "You had me at DIE, BITCH!" Cuba Gooding Jr's character would then rifle through Wuornos' purse, and say "you just showed me the money!"
2) Monster--this biopic about the actual serial killer Wurnos would have been turned into a comedy. We'd replace all the killings and violent parts with comedic sound effects, and it would be more a film about a serial killer who keeps goofing up with hilarious results! Somehow I would have gotten John C. Reilly in there, he works cheap.
3) Titanic--this movie needed a murder mystery more than anything. It really dragged, but frankly a stabbed passenger (my vote would be for Kathy Bates' character, who pissed me off anyway with her "oh look how earthy I am, like an early day Roseanne") and a Belgian super-sleuth could have livened up the middle. It'd be great because he'd solve the murder (turns out she stabbed herself while trying to pick food from her teeth) at the exact moment the boat hit an iceberg. And I'd leave in John Astor's witty comment, "I asked for more ice, but this is ridiculous!"
4) Star Wars--I know, it's blasphemous among nerds to suggest this film could have been improved. But Luke was a weak point--no character development, no depth--just pure "gee shucks" farm boy. He needs a split personality, and his alter ego--"Stuart" Skywalker--could be up to all sorts of mischievous hijinks.
5) Road House--it is impossible to make this a better movie than it already is.