Originally Posted by
Ilan Preskovsky
Forget going according to what "matters" as so much of that is crap and while Crisis is OK, it's a terrible intro to the DCU. Look for the most highly respected comics from the '80s/ '90s and take it from there. This way you don't have to plough through the garbage to get to the gold. Also, those comics from then that are still so highly regarded today are, by definition, far less likely to be incredibly dated than some random superhero comic from 1984. The best stuff is (usually) easy to find too, in trades but most of the stuff from then is on Comixology.
It also depends on what you're looking for. If you're looking purely for regular superhero comics then stuff like The Flash by Mark Waid, JLI by Giffen/ Dematteis, or the triangle era of Superman are good bets. The '80s, however, were really when DC started to grow up and along with more genuinely mature superhero comics like Batman: The Dark Knight Returns and Watchmen, you also get tons of comics that pushed the envelope with many of them laying the groundwork for the first wave of Vertigo. This includes stuff like Moore's Swamp Thing, Morrison's Animal Man, Shade the Changing Man, Sandman and Hellblazer.
There are tons of recommended reading threads on these forums. They're normally a pretty good place to start.