Ok, so if you're really into comicbooks, you've probably read most of these already, but just for the purpose of sharing, I'll list a few comicbooks I think people should read and why I think so for each one. It would take too long for me to list all the comicbooks I like, so I'll just name the important ones in the order that I think of them. Ready? Let's begin.
This is a classic Marvel story where a wide range of heroes and villains are brought to an alien planet to battle. Besides being a classic and the first appearance of the Beyonder, it tells the origin of Spider-Man's black suit, and indirectly causes Venom and Carnage to be created. I think that's important. Another little detail is that this was the first Marvel series on which action figures were based, and I like action figures, so yeah.
You have no excuse not to read Watchmen. It's a self contained story, meaning that when you pick up the book, you don't need any background knowledge of the Watchmen universe. It's pretty famous and got fantastic reviews, and rightly so. This more realistic take on superheroes (with the exception of one blue guy who controls atom:s) is brilliantly written and really makes you think.
If your only experience with Hellboy is the movies, you might not expect the comicbooks to be very deep or philosophical. However, if you pick one up, you'll find that that couldn't be further from the truth. I'm all for occult steampunk Nazis summoning demons, and these stories are written so intelligently that sometimes I even think to myself "Look at me readin' smart stuff!"
the Walking Dead:
This has to be one of the most disturbing comicbooks I've ever read, and if that doesn't hook you, I don't know what will. It really does mess with your emotions, but in a good way. The black and white art style adds interest, along with the emphasis on the character development of the human characters instead of the mindless action you find in some other zombie stories.
You're missing out if you've never read Judge Dredd. Even in its earliest days, this is a dark series with lots of murder and death, but good storytelling with a great protagonist and a dark sense of humor. People who liked the movie will like the comicbooks, and while we're on the topic of the movie, you should sign the petition to make another over here: http://2000adonline.us5.list-manage.com/subscribe?u=a6e40236aa24d482cfff600d2&id=62906ebdcc. Also, I think the idea of the world getting blown up by war and civilization only existing in large dystopian cities surrounded by radiation desert is completely possible, so we might as well read up and get ready.
Spider-Man: Kraven's Last Hunt:
Many argue that this is the best Spider-Man story ever told, and I think I agree. Just like Hellboy, it's written all smart and quotes poetry and stuff, so it has that going for it. It also made me respect Kraven the Hunter more than I thought I ever would, which sounds cheesy but it's true. Anyway, really good story, pick it up, etc.
Iron Man: Demon in a Bottle:
At first glance, this may look a bit like anti-alcohol propaganda, but I pinky promise it's better than that, and you can't break a pinky promise, so believe me on this. It depicts Iron Man at his absolute worst, having lost nearly everything, and makes him a much more interesting character since we see that the one thing armor can't protect him from is himself. Besides his internal struggle, the story also has a nice lineup of villains, a retelling of his origin, and is the first appearance of Justin Hammer.
For me, this is the classic Batman story. It has tons of villains, and is the first appearance of Bane, who's one of my absolute favorites. You may know Bane as the man who broke the bat, and this is when he does it. It also tells the story of Batman's comeback and how the cowl was almost usurped and corrupted by Azrael. This is the same kind of deal as Demon in a Bottle where the hero becomes a deeper character by falling and then rising.
And that's it. Those are the ones I think everyone who likes comicbooks should read. Regardless of what publisher or what style you usually read, all of these are worth your while.