Indiana Jones and the Kingdom of the Crystal Skull. It's admittedly been a while since I've seen it, but I thought it was quite good when I first watched it. Most criticism of it I've seen seems to fall into three broad categories:
1. It has silly scenes in it, with the nuke being the most commonly brought up. This is true, of course, but the original trilogy had their own share of ridiculous action, and the fourth had some very good, memorable part as well: the scene with the ants, the chase in Hanger 51, the alien take-off at the end, etc. People seem to focus too much on the implausible in this, overlook similarly unlikely things in the originals, and then ignore the good parts.
2. Too much CGI. Once again, this is true, and there are times when it is nigh-unforgivable, such as the jungle chase with the monkeys. But at the same time, a majority of the movie is still practical effects in actual locations - it is nowhere even approaching Star Wars I-III levels, or even a lot of other films coming out around that time. An irritating part, yes, but an overstated one.
3. It has aliens. This one I really don't understand: when I ask people about why Crystal Skull is bad, an extremely common response is just to say "it has aliens in it," and it just baffles me that this is such a huge sticking point. Yes, it is different from the originals, when Indy was hunting for religious relics, but it is also a movie meant to emulate the pulp fiction of the eras they are set in. The originals were set in the pre-WWII time of treasure hunting, tombs in the ancient parts of the world, and stories like The Maltese Falcon or King Solomon's Mines. The 1950's were the time of science fiction, UFOs, distant aliens and Cold War paranoia: the difference in time period made the inclusion of sci-fi entirely appropriate. Just because it is different doesn't mean it is bad.
Anyways, that's my account of it. It's hardly perfect, but I still enjoyed it and don't really understand the hate it gets.