RAM - the computer I had in 1983 had 3.5K of RAM (Commodore Vic-20). The computer I am typing this on has 16GB of RAM.
This, along with attendant improvements in storage - no more magnetic tapes, thank goodness - and improvements in speed is the big change I see.
Sure there are touch devices and spangly UIs, but from a developer's perspective it's all still on the command-line, right? ;-)