It doesn't get better or worse every movie, because everything in Jackass will surprise you. They had a lot of new stunts that were completely different from old ones which makes it fun to watch. If I had to rate all the Jackass movies from 1st to last it would be..
1. Jackass 2
2. Jackass 3D
3. Jackass
4. Jackass 2.5
The ending of Jackass 3D made my day. Instead of doing a bunch of random other **** in the credits, they brought back little skits from the 90s when they first started it all.