Usually you would remap the keys in each game (I'm assuming you mean PC games?). If the game does not allow key mapping then some people use a keyboard encoder's software to remap the keys (eg IPAC & WinIPAC software). This can be done manually or automatically with MAMEWAH...it should be possible to do it from other FE's too, if not by a specific feature then by using batch files.
Is that what you mean?