A good movie is a thought-provoking, cinematic masterpiece. A movie that is multi-layered on what it is trying to convey, something that makes you think rather than just nice visuals. In Spiderman, you just have to look at the screen having your brain turned off, and you'll still understand everything because there is nothing to think about.
A good movie also has a messege behind it sometimes, if not always. Movies that try to be philosophical are truely the best movies ever to exist (and are very rare, for that matter).
There you have it, a qualitive defination of the word 'good movie'. Life of good movies for me:
Finding Neverland
Tale of Two Sisters
Pulse/Kairo
Suicide Circle
Wow that's it. I thought there were more...