Here's a yearly market share graph for console manufacturers in Japan (posted by Oscar Lemaire on Twitter), spanning the past 21 years of Famitsu hardware tracking. It is mostly comprised of Nintendo and Sony. For those curious about the now gone manufacturers, Sega had the Dreamcast, Bandai the Wonderswan, and SNK the Neo Geo Pocket during the displayed period.

Nintendo is now bigger than they've ever been in the past 21 years. Or aren't they?

Wasn't Nintendo selling twice as much hardware during most of the 2000s, though?

Japan is a dying market for consoles. Once in the 80s, dedicated video game hardware survived nowhere else in the world, and now you can sell 100m of them without even launching a console there.

Nah, Nintendo's not bigger than they ever were. I haven't checked the numbers but I'm pretty sure Wii+DS sales were considerably higher than Switch sales are now. But, at that time, the PSP had a large chunk of the market. With Sony's portable line gone, Nintendo's marketshare goes up.