At least once a week, I run into some closed-minded jackass who'll make some sort of sarcastic/wiseass remark that comics are kiddie stuff/immature/and OhmyGod how can you still read those?
And sure, I couldn't give less of a flying F for ________ (insert some B Marvel/DC character) but I could make the same argument and call them out, "Oh you read books? 50 Shades of Grey is a book, ergo books are stupid and feature boring and underdeveloped characters." Or, "Oh, you like movies? Paul Blert the Mall Cop is a movie. Movies must suck!"
That out of the way, this is a quick list of movies I dug that were originally graphic novels. Sure, the comic fans knew that but your average movie fans didn't.
A History of Violence
Road to Perdition
Snowpiercer
The Crow
These too but they're not my favourite movies:
From Hell (Johnny Depp)
Red (Bruce Willis)
Wanted (Jollie)
The League of Extraordinary Gentlemen
Sin City is a grey area. More people knew that was a graphic novel than Road to Perdition for example, but not as many as I thought.