Guru? I don’t know about that. Sequential-art addicted Marvel zombie mind-slave? That sounds more like me!
Here’s the thing with getting into comics, and this is what I have told everyone that has come to me in the past (including a handful of peeps like yourself, with a burning need to Know All The Canon): You’re not going to know everything.
You’re never going to know everything. There’s just too much. I don’t know everything. I know very little, in fact. Go on. Ask me something about the X-men. The X-what? See? Nada.
The best thing to do, and this is my little trick that I personally used, is to find a character that you LOVE and use them as a gateway drug. Jump on that character’s back and follow them from book to book! It’s the best way to get into new books and introduced to new characters, while still having something familiar to cling to. I used Hawkeye and Captain marvel, which, by the way? Right now they are PERFECT characters to use for such a trick.
As for a jumping-in point? You’re in luck! Beginning in October, Marvel is doing a relaunch of several of their major titles, as well as adding in a few totally new books. This relaunch is aimed to streamline a few stories and specifically bring in a new reader such as yourself. You can read more about Marvel Now right here!
In particular, I would recommend checking out Avengers Assemble. Kelly Sue Deconnick will be taking over writing duties with issue #9 (November 2012), and the series works as a great bridge between the movie-verse and the comics-verse.
Now…Ultimates. I am loath to recommend Ultimates to any new comics reader, particularly someone with only the MCU as prior reference. What started out as a great idea, and a perfect way to introduce people slowly into the greater Marvel Comics universe, quickly turned into a total disaster. It has a few shining moments of greatness - the first two volumes are pretty decent. But the further it goes on, the more disgusting and disturbing it becomes. Captain America in particular is tainted with moments of slight racism and thinly-veiled homophobia that are hard to read.
It IS a good introduction to a lot of characters, and a good way to break into reading a comic book format. You don’t need any prior comics knowledge at all to read the series, and it was actually the first series I ever read. But if you do start with it, please, PLEASE take it with a grain of salt, and stop after Vol. 2. Ultimates is a good break-in, but it’s not very representative of the characters portrayed within.
If you want something simple to start with? I recommend Marvel Adventures. While marketed as a book for younger audiences, this series was a GREAT introduction for a lot of people. Easy stories, stripped-down and simplified characters, and self-contained plots. You can find collected volumes at your local comic store, on Amazon.com, or ComiXology.com!
GOOD LUCK!!! There is NOTHING that makes me happier than hearing that someone is willing to brave the intimidating world of comics! It’s not easy - I’ve been down the rabbit hole for about six years now, and there are still moments where I feel lost! Just accept that it’s going to happen, and remember - Comicvine.com is your friend!