Might as well just read New 52.
The old stories are great, but you'll be wishing that New 52 never happened, and then you'll have to deal with the fact Pre-52 is never coming back.
I don't care about that kind of stuff, I just want a good read
Superman 'Brainiac' is really good, Gary Frank on art, they also made an animated movie about it called Superman Unbound (haven't watched it yet)
Superman Unchained has started, it seems like it will be a good series, but if it's going to be $4.99 I might wait a month so the price will drop on comixology. Also comixology is having a sale on Superman right now, over 200 issues!
links go straight to the comics from comixology
Having read every single one of these (and a great many other Superman stories as well), I feel qualified to offer you my ordering of quality in respect to these stories (ignoring their artistic strengths or weaknesses), all of which I consider excellent in some respect, despite a low ranking on the list or any criticism I offer.
- Final Crisis (The best story in the medium of sequential art, sans Flex Mentallo: Man of Muscle Mystery)
- Whatever Happened to the Man of Tomorrow? (An excellent swan song that is truly emotionally heart-wrenching)
- All-Star Superman (The best character study on Superman, bar none)
- Morrison's Action Comics run in the New 52 (Read it at least twice in full to understand why; that's all I'll say)
- Final Crisis: Superman Beyond (This truly encapsulates the scope of the character)
- Earth-One (This cinematic tale truly captures Clark's raw intellect and offers a great take on Krypton's fate)
- Birthright (The best Luthor story would be the best origin as well if not for a meandering opening three issues)
- Secret Origin (This excellently synthesizes the best elements of what came before it)
- Kingdom Come
- Infinite Crisis
- Final Crisis: Legion of Three Worlds
- Adventures of Superman (digital first)
- Superman for All Seasons
- Superman and the Legion of Super-Heroes
- For Tomorrow
- Up, Up, and Away
- The Man of Steel
- Red Son
- Secret Identity
- For the Man Who has Everything
I'll get to the rest of my summaries later...
I think All star superman isn't a good superman story to start with...
try Morrison's Action Comics,Kingdom Come,red son and for tommorow for a darker superman.
EDIT:Also i have a Superman recommending reading for this :
Of those, Birthright is the closest in plot to MoS. If you want more Zod, Superman: Last Son by Geoff Johns and Richard Donner is pretty good.
All-Star Superman and Kingdom Come are both awesome books that present a super iconic and a post-modern Superman respectively. Red Son is good and can be read to show how important Ma and Pa Kent were in shaping Clark into the hero he became. For the Man Who Has Everything and Whatever Happened to the Man of Tomorrow? are written by Alan Moore, that should speak for itself.
All the others are good and you should read them if you get the chance.