Also if you're not only interested in Marvel and DC, I would heavily recommend Mike Mignola's Hellboy, which I'm sure you've heard of.

Another comic, similar to Hellboy, is called Atomic Robo. Volume One came out recently, which is a compilation of the first six or so comics, and it's around 200 pages for like $15. It's written by the guy who makes 8-bit Theater, and the art is really nice too, so I highly recommend this as well.

I'm too impatient to read the whole topic so I don't know what advice you got besides good shit like Watchmen and others...
Now, about regular superhero comics... I WILL STRONGLY RECOMMEND AGAINST READING REGULAR CONTINUITY BOOKS.

The reason is that due to the constant change of writers and other stuff, they usually suck balls and are pretty dumb. And when they not, they usually fire the writer and the new one will make sure he takes care of the character becoming dumb. (For reference check Morrison's run on the JLA and compare it to the latest JLA... (Morrison's is v3, we're on v4 now I think)

I will, however, recommend certain lines of comics and generally specials can be good.

1) Elseworlds are good. Most of them are pretty decent, basically stories in where characters are taken out of their setting or where something in the setting changes enough to affect the story... Some are pretty ingenious.
2) If you want to get into Batman... Read Batman Year One and then check the entire Legends of the Dark Knight series (I think it's 214 or 215 issues)... This series is basically short stories (Anywhere between 1 to 5 issues each, usually 3) by different writers and artists... The stories are generally non-chronological, non-canon and self-contained... Some of the greatest Batman tales are on this series. I will also recommend important landmarks like Batman: Images and Batman: The Killing Joke, both about the Joker.

Also... Try the new "Joker's asylum" series... In it, the Joker basically narrates a story about himself (In the first issue) or another villain in subsequent issues. I've read Joker, Penguin and Poison Ivy so far... And all have been atleast above par.

For the Justice League, like I just said before... Check the JLA v3... It's in my opinion the best incarnation.

Do not read Batman year one. It may be millar's best comics but it's not up to Batman scratch(it's Sin City in pointy ears). Killing Joke, Death in the family, Arkham Asylum, Hush and Venom are great.
Morrison's JLA is the best run it's had for sure. New World order and Rock of ages being prime examples of books to pick up.

And all have been atleast above par.

i never understood this phrase.  shouldn't it be below par because in golf above par is losing?

i never understood this phrase.  shouldn't it be below par because in golf above par is losing?

Above is generally accepted to mean "better", so you could substitute above with better.