While I agree the C64 palette is better than the ZX Spectrum palette, I find some of the colors rather drab. I much prefer the Atari 800 palette of 256 colors.
Normally, the Atari can only display 4 colors per screen, not counting the player/missile graphics (aka. sprites), but a few low resolution modes allow either 16 luminance levels of one color, 16 colors at the same luminance level, or 9 colors of your choice.
Then there are software modes. One option is to change the palette every scan line. Other software modes allow alternating between two or three palettes on each screen refresh, allowing more than 256 colors.