I can stick through just about anything. Heck, Orson Welles' The Trial - unwatchable for some of my friends - is a personal favorite of mine. But it was only a few months ago that I first walked out of a theater midway through a screening, completely bored. It was Taken 2. What could've been a fun Liam Neeson-sploitation flick was just a joyless affair, churned out with the sole purpose of making money based on the success of the previous film. I went to the bathroom after the first half hour, and never returned.
It's sad, because even money hungry sequels are capable of delivering something entertaining. Take Ghostbusters 2: not needed whatsoever, but did a fine job of continuing the story and gave audiences something to come back for. The cast/crew weren't phoning it in and the filmmaker wasn't filled with contempt for his fans. It was a fun movie that I would pay to see, even now.
I wouldn't even scoff at a discounted DVD of The Hangover Part III. It really isn't worth any attention whatsoever.
