I do enjoy the first, and I'm sure I nearly wore down my DVD from playing it over and over. I don't care that you were made of hate, Shrek, you'll always be love to me.
Second one was absolutely hilarious. On par with the first at least, still debating internally over which is better/
Third is the worst. Riding off the coattails of the second. Not even a new villain!
Fourth, while forgettable, is not nearly as bad as the fourth and has a much more interesting if somewhat wasted plot.
Puss in Boots I've not seen more than 5 or 10 minutes of. All I know of it is the Lady Gaga song "Alejandro" that plays in it. That alone excites me though.