I think I can best illustrate why 4E feels more like "the D&D I played in 1984" to me than anything since with two negative examples.
3E lost me when DMing became an exercise in trying to out-rules-mastery my players in order to have anything like a challenge. The systematization of every aspect of play became a straitjacket for creativity and collaboration.
2E lost me when DMing became an exercise in leading your players by the nose through an elaborate setting full of niggling details - most of which the players might know better than you do, since they were all in mass-market novels. The "canon-ization" of every aspect of setting and flavor left PCs and DMs alike walking on guided tours through an art museum.
4E (at least so far) replicates the sense of "you can do anything at all" that I remember from the old days. Sure, there are lots of rules - but they pretty much only touch on the places I *like* having rules, and the flavor text is eminently separable from the numbers... plus, for the first time in a long time, both DM and players are explicitly encouraged to improvise, re-skin, and make it up as they go along... and actually given some useful tools for doing it.
So to me, 4E is most of the things I liked about 1E and before, plus a whole box full of useful new tools & toys.
Then again, I really don't recognize the flavor of "old school" gaming that the most vocal partisans of it advocate. That's sure not how we played in the 80s.