I agree with a lot of the recommendations. I've only been reading comics for about a year and have enjoyed quite a few of the stories I've read.
Several that weren't mentioned are:
Superman: For Tomorrow - It's got beautiful art (Jim Lee) and a thoughtful and compelling story that gets a little odd, but I really enjoyed it.
Superman Unchained - New 52 era, so he and Lois aren't together but they are still friends. It deals with the issue of why Superman doesn't submit himself to earthly authority. Again, beautiful art and I enjoyed exploring that idea.
Superman: Mann and Superman - a great graphic novel about power and responsibility
The Adventures of Superman (2013) is a collection of small stories by tons of different authors. One of my favorite stories ever is in this volume, called 'Faster Than a Bullet". The art is mind boggling good, the story is about how Clark saves the world 5 times before breakfast, but his idea of a perfect morning is... (not gonna spoil it)
Superman/Shazam: First Thunder is outstanding
Superman/Wonder Woman: Whom Gods Destroy is an elseworlds with a good story but I thought the art was kinda ugly
But even with ugly art, the story was still good enough to make it to my favorites list.
A couple of things of note:
Superman: Peace on Earth is very good, but very hard to find right now because I don't think it's ever been reprinted. That's about to change. A trade is going to be released in December with it and it's 5 companion novels collected. It's called Justice League: World's Greatest Superheroes by Alex Ross and Paul Dining. The companion novels are quite good as well, so it should be worth the cost, and it might be available on your service too.
If you like digital comics and are looking for a good place to buy, Comixology.com, an Amazon site, runs sales every week on different stuff, and those sales usually transfer over to Amazon Kindle too. I buy everything usually for $5-6 on Kindle and it unlocks on comixology also. Kindle is convenient, the comixology version has better resolution though.
Also, I own the Lois and Clark collection that's mentioned here. It's got a great forward in it by John Byrne about his thought process when he was reimagining Superman. If people are interested, I could probably be convinced to scan the pages of the forward and share them
