Jumping into the 'classics' discussion, I think one of the strengths of cinema as a medium is that there are so many different ways you can appreciate a film that the 'greats' usually have multiple 'entry points' you can pick up on based on your own tastes.
For example, I would recommend Rope, Rear Window or Dial M for Murder as 'gateway' Hitchcock, because they don't have the cinematographic set pieces, but they deliver the suspenseful plots in spades - but then I'm a sucker for theatrical type stuff, and will always watch a 12 angry men if its on, or pretty much anything written by Mamet or Sorkin
Psycho I think is a victim of its own renown; the shower murder isn't a plot twist in the way something like The Sixth Sense or Soylent Green have, its much closer to a full genre subversion in the way something like From Dusk Til Dawn does, and knowing its there completely changes how you approach it.
As with most capital L literature, a surprisingly large amount completely holds up, you just have to approach it with curiousity rather than the feeling it's something you're supposed to like because everyone says you should.
e: oh, if you want to see Welles killing it on a purely
actor level, check out The 3rd Man