None of them are about graphics. Physics engines are all about how things move. (Optics, electromagnetics, thermodynamics, and plenty of other physics topics aren't physics to gamers, as I understand it.) So the motion of solids, fluids, and cloth are the big ones.
The first car explosion I remember that actually had bits flying off was in City of Heroes' 'hazard' missions, where they had your villain run around town smashing stuff. You could smash a car and BOOM! Wheels fly off and various other pieces go flying - how many depended on how good your CPU was. You were best off with a dedicated physics card, though. Now'a'days we can kick over bikes and not think twice about it.
Physics engines could use a lot more work, too. Waves on water look a lot better now but are still too regular. I haven't ever seen a believable surf hit a beach.
I would consider all of those "graphics", unless the pieces that come off of the car have an impact on the gameplay. Wavy hair and clothing is all physics too, but is just there to make the game prettier.
Happy to be corrected, but I'm happy to No True Scotsman touch screens and float away merrily in that bubble.
I agree, touchscreen controls, while a major innovation for the gaming market as a whole, have not had a big impact on PC or console gaming.
If you went back to 2005 and showed someone from that time some of the games we have available now their minds would be totally blown.
But what would their minds be blown by, besides graphics and scale? That's really the core question here.