moslo or one of the others might do it for you...
but generically no... You could underclock the processors... but I don't think that will work...
other emulators have done it in the past... but the real solution is practice at the game until you want it speed up! Lots of the fast pace games are zen type games... You get into a rythm that you can react before you can think...
Arcade + nervana? Arcadevana?