Having owned CPC, C64 and a ZX, I must say I have the most affection for the CPC464. I learned BASIC programming on it, and had a 64K extra RAM Pack, Multiface II plus OCP Art Studio and Genius Mouse! The colour monitor was awesome too - no fuzzy TV picture!
To be completely honest, some games were just better suited for one of the platforms in particular. I'd find it difficult to say that any one machine was miles better than the others for games. For example, CPC was awesome for Captain Blood, Cybernoid 2, Dizzy Games and Chase HQ while the C64 was better for Last Ninja 2, Bubble Bobble, R-Type and IK+
I have fond memories of the Speccy although in honesty I did sometimes prefer the CPC versions of many games that were available on both.
BBC was fun at school... loved Repton 2 and Chuckie Egg!