the number of the MSX computer produced

Check the Wiki for the Daewoo consoles:

https://www.msx.org/wiki/Daewoo_CPC-50
https://www.msx.org/wiki/Daewoo_CPC-50A
https://www.msx.org/wiki/Daewoo_CPC-50B
https://www.msx.org/wiki/Daewoo_CPC-51
https://www.msx.org/wiki/Daewoo_CPC-61
https://www.msx.org/wiki/Daewoo_CPG-120
https://www.msx.org/wiki/Daewoo_DTX-1493FW

They were very popular in Korea and even now, fans still create FGPA-based machines, inspired by some of these consoles.

History rewtitten here on the spot. While you'te at it, please also solve Quantum Theory, because "my guess" is you're not far off.

Have fun ;-)

The function of the Z80 in the megadrive is a bit more like a controller than a processor in utility, due to the limitations of bus access down to very critical access slots. but it is indeed a full processor in practice, you branch binary execution through a RAM port on the Z80 to get it to run small processes that act like sound drivers.

Saying the Megadrive is a z80 based machine is a pretty big stretch though. It technically has a z80 that is programmable, but the architecture of the system is such that everything runs through the 68000's memory space. You can't access the VRAM memory ports from Z80 RAM, for example. Everything is done through the 68000 primarily. Upon booting the machine, the primary execution vector for binaries always begins in 68000 memory space, for example.

As for z80 based gaming devices, I'll say that the TI-83 line of calculators have been in constant use for like 30 years now, propped up by the USA education system. It's 2020, and they still require you to buy a TI-83 calculator despite kids having tablets in schools, haha. I definitely wasted so much time playing Tetris on my calculator instead of listening to my geometry teacher back in the day, though, lol. Those calculators must have seriously sold into the hundreds of millions of units by now, considering virtually every school child in the USA going back 3 decades were required by curriculum to have one. The best numbers I can find are from Texas Instruments themselves back in 2003, where they said they had sold about 25 million z80-equipped TI-83s in about 7 years going back to 1996. In those early days, the calculators were largely optional, it was with a bunch of big reforms to US education around 2004 with the introduction of the TI-83+ that they became mandatory for primary school math, so the majority of their sales would have come in the following 17 years, after their reported 25 million sales. So, like I said, my guess would be they sold probably over 100 million TI-83 calculators by now.

An aside about the TI-83, though, the most recent revision actually removed the ability to execute z80 assembler binaries which has upset a lot of people.

This is not correct, the Megadrive has a control signal in its cartridge port that makes it behave like a SMS, if I remember correctly when B30 is low the Z80 takes over the bus and the machine becomes a SMS/Mark3.
Sure, the Z80 can't control the 68000 peripherals, but it has its own.
During the console life, this 8 bit mode was exploited by disk copiers to bypass the TMSS protection, save on parts (just one 8 bit wide Eprom to run the copier) and offer some compatibility with the SFC (the pro fighter copiers worked on both MD/SFC) .

Yes, I think the same, but then one could object that the Amstrad PCW (probably CP/M best selling machine) was sold as a typewriter and not as a CP/M computer.

I also was an avid TI-83 user in the late 90s and early 00’s . On my school it was introduced together with the "2e fase" school system. I even made a transfer program for MSX to cross-develop and transfer programs to the TI-83 with the MSX!