F Zero GX runs like trash :p

[Shonumi]

Simply because you can run some games at 60 FPS in no way means you can run any other game at that speed. Games in Dolphin have different demands on the hardware. Somee need beastly hardware, others will run in your kitchen toaster. F-Zero is a fairly demanding game, so any slowdowns are likely because of your hardware.

Try the latest development build (4.0-2XXX not 4.0.2) The stable builds are older and actually slower. If that still doesn't help, post your PC specs.