I'd have to say The Hunger Games. It was a good enough book, but I didn't think it transferred to movie well. Not to mention, it's really confusing if you haven't read the book and aren't sure what it's about. It doesn't really bother to explain much of anything that happens.
I'd also have to agree about some of the HP films. I thought 1 and 2 were pretty well done, and part 1 of number 7 was decent, but the other ones were either mediocre or downright bad.