Realistically, I think the better question is what are the 3D Bluray's to avoid. Reason being, the vast majority of stuff that I have seen have been Amazing. Each movie I see seems to be better than the last one. I've only seen a couple of things that were kinda lame. Dinosaur's Alive was probably the worst one that I've seen. I can't really think of anything else that was lame. I've seen some of the demo disks, and certain things on some of the demo's were lame, but for the most part, every movie that I've seen has blown me away with the crispness and clarity of the 3D Blu Ray image.
Here are some of my favorites so far:
Ice Age 3
Alice in Wonderland
Grand Canyon (didn't like the narration or story though)
Avatar demo clip
Monsters vs. Aliens
I have not yet seen Polar Express, Christmas Carol or Cloudy with a chance of Meatballs.
I have seen How to Train Your Dragon, and actually I didn't think that it was the best example of 3D. Most of the movie has outstanding 3D, but there are alot of scenes in the dark that aren't as flattering imo.