Megadrive and Mega CD. The whole 'Mega' thing makes it sound really....Mega. Therefore making it sound interesting; a good name for many reasons. Thinking about it, we'll also include MultiMega and WonderMega in there too.
Super Famicom. Even to this day those words still sound so cool. And a UK SNES may look exactly the same as a SuperFami, but it's those important words on the front of the console that make all the difference.
Dreamcast. Cool name, another bit of good marketing.
Can't think of anymore that I'd count as really good. Although these Chinese pirate mateys seem to come up with great names for Famiclones.