An 030 makes Grand Prix the finest racing game on the Amiga (with the F1gp patch). I found it unplayable even on an 020. I get about 20fps with my 030/40 and the game is suddenly a LOT of fun.
SimCity 2000 is unplayable even on an 060. Granted it does get closer to playable, but I remember playing the game running smoother on emulated MACos on my 060 then in Workbench 3.1 on the same machine.