It comes down to how those games compare to the competition, I think. The TG-16 RPGs are legendary, Lunar-quality type stuff (but with GBA-caliber graphics and sound).
"It" comes down? What is "it" -- your opinion of what deserves to be translated? You're entitled to that, but the question was how many untranslated RPGs there are on the Sega CD, not what you think deserves a translation. (You claimed there were "a few", I noted there were nearly 20, and now you're moving the goalposts.)
If you're not interested in those, that's fine too. But it seems like you're trying to actively discourage
people from translating games you don't deem good enough -- or on systems you don't deem worthy -- and that's not cool.
Personally I think your opinion of the PC Engine RPG library is a bit overstated (and a few other adjectives too), but if you were to translate some untranslated PCE games, I'd be the first to congratulate you. I'm all for people putting their money where their mouth is.