Posted By:
Jason Lno one has really outlined what it takes to BE a classic set!
I just found this thread, for some reason I skipped it, but I do love this kind of topic.
From what I gather from the posts above (and my own preferences, because let's not forget those!), a classic set would require some of the follwing attributes:
-A great, attractive graphic design
-issued in series
-should contain a few key cards, either rookies or very desirable hard-to-gets
-should be connected to your childhood collecting 
what else?
I would add:
1) 1978 Topps (simple borders, game on back, Murray, Trammell, Molitor, Murphy rookies, Dawson's second year)
2) I would add to the 1984 Donruss, the 1985 Donruss. The factory fresh set is absolutely gorgeous, and has Puckett and Clemens rookies
I would agree, that if you were to label sets liek we do with the name "key card" I would call the 1984 and 1985 Donruss, along with the 1984 Fleer-Update as the key sets of the 1980s
In fact, that might be an interesting debate to take it one level up: What are the "Key Sets" from each decade?
1950s: 1952 Topps, 1953 Topps, 1953 Bowman Color, 1957 Topps
1960s: 1961 Topps, 1968 Topps
1970s: 1975 Topps, 1978 Topps
1980s: 1984&85 Donruss, 1984 Fleer Update
1990s: who cares?
2000s: Heritage, Allen & Ginter
thoughts?