I am actually very familiar with the Deadpool comics, because I like the comic character a lot, and I have read a number of his comics. However, I did not like the movie all that much either, but it is because I am too familiar with the character.
Now, to be fair, the movie does capture the spirit of the character, and it does stand out amongst tidal wave of superhero movies, because it, like the comics, goes for lowbrow comedy first and foremost, and that is pretty much the essence of comic books. However, I find that the filmmakers actually did not go far enough. In the comics, Deadpool goes insane due to the experiments to cure him of his cancer, so his antics is a lot crazier, and a lot of times, sadistically bloody. Thus, Ryan Reynolds' take is really tame, and only barely scratches the surface of who the character is. That said, the movie will never be made if it is a completely faithful adaptation, because it could very well be seen as torture porn, so I understand why the filmmakers really watered it down, but that does not mean I am not disappointed though.
My main problem with the movie is the treatment of Death. Deadpool is actually in love with the personification of Death, who he saw and fell for during the experiments, but because he cannot die once he got his healing factor, it becomes a case of star-crossed lovers, which is a really interesting take on the concept, and gives the character even more depth. Then there is Thanos, the god-like villain shown in the Avengers series, who is also in love with Death, so he curses Deadpool with life, a sort of immortality, which, again, gives the character another interesting angle, since that means Deadpool can be tied to the Avengers franchise. Unfortunately, that aspect is completely omitted, and not even hinted at, in the movie, so that is a big missed opportunity, which has so much potential.
Despite my misgivings, I will probably still go see Deadpool 2 next year though. Mindless fares have some merits, and it is different enough to warrant a trip to the theatres.