You know what may well be a weird deal-breaker for me:
The light spell.
I have had exactly two experiences with real-world 'dungeons', and those were enough to convince me that the seemingly-banal issue of light sources is actually a huge deal. In one of them, our guide switched off her torch to let us know what it was actually like down there, and what resulted was a darkness unlike anything I had experienced before.
(And when we "split the party"? That was actually scary, being unable to see anything. And all that had happened was that she'd gone around the corner!)
But 4e gives Wizards light as an at-will power. And Pathfinder lets them cast 0-level spells at will, including light. In doing so, both games utterly trivialise the issue.
So, yeah: bring back light as a strictly limited-use resource, especially at low levels!