You say "now" and "then", referring to the 70s - but if we go a bit further, would you say that there is any difference between, say, "Commando" and "Shoot 'Em Up"?
Both are silly and over-the-top, and have psychologically flat characters - but could anyone in their sane mind say that Clive Owen and Paul Giamatti weren't "memorable" in those roles? Boy, they WERE.
Then you got stuff like "Welcome to the Jungle" from a few years ago - basically a "modern" "shoot the bad guys" action schlock movie with hammy villains and badass heroes with sidekicks - old concept. Would you say The Rock was boring, or Seann William Scott were "forgettable"?
The whole film thrived on the witty dialog, ideas and performances. Now I'd bring up Chris Walken, but that guy makes gold out of every piece of shit movie he's in, so he's not that much of an argument, LOL. Generally, lots of bad movies have cool villains so that kidna doesn't count - take Robert Carlyle from Eragon... awful movie, UNFORGETTABLE evil wizard.
Again, we're talking about entertaining action films, so it's not about deep psychological characterization (of which there's hardly any in ANH, and not terribly much in the sequels either), it's about entertaining and memorable main characters.
Is there REALLY that much of a difference between "then" and "now"?