As stated it is so hard to nail down a specific "Rock" album as an illmatic, Ready to Die, even a Marshall Mathers LP, or The Chronic.
Hip Hop/Rap have a few sub-genres with the fast rhymes and joke stuff, but for the most part it is all about rhyming or a flow.
Rock doesn't really have that, and I am including everything under the rock category here. You have Metal, which has a bunch of sub-genres(Speed/Death/Heavy/Hair/etc.), but that is still rock music.
Punk is in the same boat, and so on. You can't nail down what is Rock music. Most "Pop" music is under the rock category if you get down to it(exceptions being maybe someone like Britney Spears)
I can't tell you what the icons really are as some people will love it, others will despise it(to be a hipster or not, who the hell really knows).
Something like Pet Sounds by the Beach Boys is considered iconic, but if you don't like a cali-rock style, you won't like it, even if everyone says it is a classic.
I personally don't love Zeppelin, but know what they brought to the genre and respect the. I just don't personally listen to them much.
As for some people not mentioned here that you might look into.
Elvis Costello(early stuff like My Aim is True up to Spike or so)
Rolling Stones of course
Neil Diamond(early. before that America song)
Billy Joel- Piano Man
Buddy Holly
The Killers(after the first album to be honest, which is good, but is outside of a the singles and maybe one or two tracks iffy overall)
The Police
Frank Zappa
U2(early)
Roy Orbison
Rush
David Bowie
Meat Loaf(Bat out of Hell(I and II))
Obviously there are more who are as good or better, but working from these you can see who they influenced, or influenced them.