I think "Shrek" (the first movie) was the most original, because it was a perfect parody of fairy tales. "Shrek 2" and "Shrek 3" were very entartaining for sure, but once I saw them, I never itched for other views.
I watched "Shrek" (1) many times, instead.
This new movie doesn't attract me so much, but I'm sure it will be a blockbuster...