1) Kingsman. The most re-watchable of all these films - I love this movie. It's hilarious and has innovative and enjoyable action scenes that manage to make Colin Firth believable as a super-badass (which can't have been easy).
This one's my favorite, although not the best film (in terms of real quality).
2) Civil War. A really great cbm, good characters, superb action and strong performances. However, as much as I love this movie I really feel it shouldn't belong in this list as it bares only the smallest resemblance to the original Millar comics - far less than either Kingsman or Kick Ass.
3) Kick Ass. Another great Matthew Vaughn film, entertaining and it nicely blends teenage angst with humour and ultra violence. I've re-watched the last 30 minutes over and over as the action scenes are so enjoyable.
4) Logan. In terms of being taken seriously as a drama this is the best of the bunch. However, I find it too bleak to have much re-watch value. It's far and away the best Wolverine film, but I just find the ending sad when I feel it should have been uplifting - not that Logan needed to live, I thought it great they killed him off, but he could have gotten over himself so much sooner.
5) Wanted and Kick Ass 2.......well they are pretty forgettable. Wanted bears almost no resemblance to the comic, and really shouldn't be considered. Kick Ass 2, well it just wasn't very well done - makes you wonder what Kick Ass would have been like if it hadn't been directed by Matthew Vaughn.
Having said all that I actually don't believe that changing/adapting Millar's work for the big screen has been a bad thing at all. The violence in Kick Ass and Kick Ass 2 was toned down significantly (and the rape of Katie Deauxma was thankfully taken out) - and yet still these are incredibly violent films. I'm not a particularly squeamish person, and I love a good fight scene (gunfight, swordfight, fistfight, I don't care) but I find some of Millar's comic work overly lurid. It crosses over the boundary into an area I can only describe as bad taste -
This is something that Vaughn managed to avoid doing when adapting Millar's work - the Church scene in Kingsman being a great example of Vaughn portraying ultra-violence in a completely brutal but also cartoonish way, almost like Monty Python's famous "Black Knight' scene from the Holy Grail film.