Most 3D polygon based games will benefit from speed and that includes games like Zeewolf and Virus/Zarch as well as your typical driving, flight and space simulation games. I don't know if there other examples but Battle Chess performs the AI opponent moves faster.
I'd find it hard to justify the price of the 40Mhz version personally and if low end 3D gaming isn't important to you then if the ACA1221 is available it would serve your purposes well.
