R-Type port for C64 was quite a fiasco. I knew the story about the original version programmed by a different team. A good R-Type clone for the beloved is in my opinion X-Out by Rainbow Arts released in 1989.
ZX Spectrum port is good, but I always hated the Spectrum monochrome graphic and I always hated some "ZX to C64" ports. I recall Skool Daze and always thought: "What cool game could have been this classic using the power of multicolor C64 gfx?"...