The CPC was a great machine when the developers were actually coding for the CPC. The easy option was simply to convert games from the ZX to it and they were killing it. Same Z80 code, same graphics in Mode 1. I have seen games on the CPC that were so much better than the C64 or Spectrum versions. For example, checkout Chase HQ, Robocop, Operation Wolf, Gryzor, Pang and so many others
And just to prove how good some games could be on the CPC, see this remake of R-Type compared to the original crap onehttp://www.youtube.com/watch?v=C_GDjT1tivo
Also, see Xyphoes Fantasy... I think one of the best games for CPC even though it was made when the CPC market was really small. Shows what the machine was capable of (they even managed to use the sound chip PROPERLY)http://www.youtube.com/watch?v=Pe3RfKKhokM
The C64 also had some amazing games. System 3 were doing miracles. SID was (and still is) one of the best chips used in a home computer.