Although Frank Miller produced the ABSOLUTELY HORRIBLE movie adaptation, the comic series was created by Will Eisner. The comics spanned several series, collections and one shots over the years, with different writers and artists, catching up would be hard to do.

anyway, here are my personal favorites. at least what I can think of right now.

Pride of Baghdad
Usagi Yojimbo
Sandman
Runaways
We3
Persepolis
Road to Perdition series (including Purgatory, Paradise)
Laika
Asterix and Obelix (lol)
the others which are already mentioned by previous posts, are pretty good recommendations too.

I tend to avoid superhero comics, because I really have no idea where to start