I agree that Tandy Color 3 is capable. But it is rare. How many programs are in software list especially for CoCo 3? King Quest II for Tandy shows good but almost static pictures. I didn't note any sound.

It looks like C64 graphics with only one or two sprites and a bit more colorful. However I could name CoCo 3 as the best 8-bit computer for King's Quest II.
MSX2+ and turboR are Japanese rarities. They have too little software which uses their advanced features. The same is true for Amstrad CPC6128+, Sam Coupe, and other 8-bit computers after 1987.
Theoretically MSX2 can be better than C64, C+4 or Amstrad CPC. But practically I don't know MSX2 games which are superior to C64 games. C64 sound is better than even MSX2+ sound. I also don't know photo graphics shown by MSX2 system which are better than C+4 pictures. Is MSX2 capable to run a game like CPC6128 Pinball?
I agree that ZX Spektrum deserved to be the best by the best price.
It is also worth to mention that BBC Micro has built-in network support and it makes it the best for this feature.
It's very difficult to make a list like that without having tried all 8-bit computers, so I'll assume that the list is "best 8 bit computers that I've used". You've completely left out the Atari's for example. Is this because they weren't best at anything or because you've never had one?
I met Atari at the 80s. It didn't impressed me much. Just yet another 8-bit computer, a bit better than ZX Spektrum. Do you name any Atari 800 feature that makes it the best?
Considering recent output from Targhan and Rhino with improved graphicmodes with more colour at higher resolution, I think the Amstrad CPC should be considered for all these 3 categories
I hope to see CPC6128 showing pictures better than Commodore +4, with sound better than C64 and with the fast hardware sprites.