I recently saw two movie adaptations of very good comic book properties. Both of them are based on works that were created by the God of Comics, Frank Miller. That's about where the parallels end though.
The first was Elektra. The movie was not based on a particular story from any of the comics that featured the assassin character that Frank Miller brought to life. This is the second time she's been on screen, though. Much like in the comics, we (as a movie-going audience) were introduced to her in the Daredevil movie. I found Elektra enjoyable, but I was pretty happy I caught it on Netflix instead of braving the theaters. Jennifer Garner does a decent job, but the character feels watered down. I don't know if that was her, or the writing or the direction... but suffice it to say, comic book Elektra could kick movie Elektra's ass.
Sin City, in contrast to Elektra, involved the creator of the original material. It was ripped straight from the graphic novels and flung up onto the screen in all it's black, white and red glory. Robert Rodriguez lead the directing duties (along with Tarintino and Miller) and it's obvious that Rodriguez got what Frank was doing with his books because I have NEVER seen a comic book so perfectly and faithfully adapted to the big screen.
I absolutely loved this movie. Besides being based on some of my favorite comics, it's a wonderfully conceived, shot and constructed film.
Oh yeah... And, Marv could kick both comic book Elektra's AND movie Elektra's collective asses.