Did the CPC ever get any sort of attempt at DK Jr? I haven't managed to track one down yet and it seems a weird omission given how completely stunning Ocean's port of Donkey Kong was.
Donkey Kong was interesting as Ocean's partnership with Nintendo went south not long after it. Mario Bros got a release a few months later but it was an underwhelming release and didn't sell well. Granted Mario Bros wasn't the most exciting game on the planet (and it ended up being rehashed as a bonus stage in Super Mario Brothers 3).
So Nintendo and Ocean went their separate ways and no other Mario games made it to the Amstrad.
To make things even more interesting. Neither Kong Strikes Back, Mario Bros or Donkey Kong ever made it on a compilation release or a budget label (other than Donkey Kong on an Erbe compilation in Spain). So you either got the original releases of these games, or you missed out.
The C64 got a conversion nearly 10 years ago, based on the Atari 8-bit version.
I reckon the Amstrad could handle it.