I also think the new Stern games are just that - "new". They have more complex DMD animations, LEDs in the playfield, newer themes to draw people in on first play. Then the more complex rule sets keep the hardcore players happy.
I actually don't like many of the newer Sterns (GB and LOTR being notable exceptions) but they are definitely flashier and deeper. I think I fall in the middle currently - experienced enough to get perturbed about the build quality but not a good enough player to be able to appreciate the deep rule set.