The first Shrek was pretty good and Shrek 2 was an excellent sequel, Shrek The Third was rather forgettable and I can't really remember much of it outside of the high school scene and the ending bit. I actually did like Forever After however since it felt more like a bizarro-Shrek fanfiction and less of "another Shrek movie".
I'm still somewhat fatigued from reboots, but I guess it isn't ogre yet.