Quoted from ccotenj:ALL extant em's are "rare"... and someone will "desire" a title, whether or not someone else thinks it is desirable or not...
It depends upon your definition of "rare". An average production run for EM games would be anywhere from 1000-7000+ units. In the last 10-15 years, production runs for modern games are probably a lot less on average.
A game like CSI or Big Buck Hunter is probably a lot more rare than Royal Flush.