Dirty Harry - Close to perfect for what it was. But I wonder if there was an alternate ending to this movie - I remember the back of the old VHS tape of this at my video store having a picture of Harry pointing a gun at Scorpio while his back was against the school bus, a scene that was obviously not in the movie.
Magnum Force - The worst of the five. Great concept on paper - Dirty Harry taking on crooked cops that are offing criminals - but the actual movie just dragged on and felt like it went on forever.
The Enforcer - Average Dirty Harry movie. As mentioned, it lacked a strong villain and that hurt it a bit, but it was still an enjoyable film. Better than the previous film for sure. I was glad to be some continuity from the first film with the returning LT. and everything.
Sudden Impact - My second favorite. I loved the dark storyline and the fact that there seemed to be two "villains" - the woman doing the killing, who Dirty Harry is after the whole movie, and then the ones who turn out to be the real villains, which is the main guy who raped her (and his buddies.)
Dead Pool - Enjoyable movie. Had an interesting plot and it's better than the second film but not quite as good as the first and fourth. It's tied with the third movie as far as rank goes.
I also wanna say that there was an actor who played a part in four movies in a row. The guy that Dirty Harry shot in the bank robbery scene near the beginning of the first film also played a murdered pimp in the second movie, the guy Harry talks to about the porno place in the third film, and then Harry's murdered friend in the fourth. This bugs me since I assumed all the films take place in the same universe, and yet having one actor play different roles in four different films kinda ruins that.
I'd rank them as:
Dead Pool/The Enforcer