I have a bit of a soft spot for the TG16. It's a pretty cool system, and is even better if you region mod it. It is expensive to collect for, but the Japanese versions of the games are usually cheaper, even with shipping. That's where the region mod comes in. As far as the library goes, Genesis wins easily. But I generally like weird stuff like the TG16, CDi, etc.
You can't compare the turbo grafx with the CDI since the CDI has no good games at all. All games are bad and even the best ones are really mediocre except for dragon's lair.
Besides in Japan it was a very normal console alongside the snes super famicom however in Japan the sega genesis/megadrive was the console that was pretty uncommon in japan while in the western countries it is the turbo grafx wich is uncommon.
I think his comparison is more in the vein that the TG16 was the odd man out system here as were systems like the CD-i, Jaguar, 3DO, etc. Yeah it was more mainstream in Japan, more so than the Mega Drive, but I think in his reference he was talking from the US point of view. One COULD tap into the PC-Engine market if they knew how but that doesn't mean everyone did; at least back then before the days of the interwebs.
My personal experience was seeing screen shots of games in magazines like EGM and running up long distance rates calling places in the back of the magazines hoping they had the titles in stock.
As for the CD-i having no good games, I'd largely agree as most people only focus on the Mario and Zelda games for it.