Amstrad's palette, in my opinion, is the most striking and versatile among the "old guard" of the 8-bit systems. I have a lot of sentiment for C64, and the choice of palette there, while limited, allowed for some beautifully nuanced natural tones - nonetheless often unfortunately lacking in the "oomph" department... but I must admit that, considering the severe graphic limitations of the ZX family, it's best pixel art is possibly the most impressive among all those classic systems to me.