Buzzfeed has a great list of the 60 must read comics your, er, must read at some point. I won't get anywhere near that number. Unless you've got a subscription to Marvel or Comixology these things are hell expensive to collect. But the list is interesting, and does have a couple of dozen I could be tempted into buying. The Communist Superman one, above, is a fascinating idea. I'm sure that future gonzo sci fi one Orin keeps trying to get me to read is also in there somewhere. And some, such as Watchmen, and Life in Hell, I've already enjoyed.
Life in Hell made me laugh out loud more than any book, ever.
Link's here. Worth a book mark for a boozy late night browse.