The Last Ninja series on the C64 sold 23 million copies.

[Bofferbrauer2]

JWeinCom said:

https://archive.org/stream/retro_gamer/RetroGamer_018#page/52/mode/2up

"The original Last Ninja sold a huge amount of units - I think it reached 4 million on the C64. Ninja 2 came out right at the point when the C64 was at its most successful in terms of sales, and sold 5.5 million copies. If you take that into context, it’s estimated that around 20 million C64S were sold, so one in four C64 owners bought the game."

Back in 2005, he put the combined sales of the three titles at 12.5 million (he says three million for the third later on). I think it's safe to say that it has not sold any more copies since 2005. The remix of the first existed at that time, so there's no reason he wouldn't have included it then, especially if it sold so incredibly well (over 10 million if the 23 million figure is to be believed).

There are a few potential explanations, but the most likely is simply that the dude is exaggerating. I wouldn't even take the 12.5 million figure too seriously. 

I do think he added all platforms together to get to 23M. While it started on the C64, it was also on a slew of other platforms:

Spoiler!

The first one alone was already on Apple ][, Apple ][GS, Amiga, Atari ST, PC, BBC Micro and both Acorn Electron and Archimedes. The second one added NES, ZX Spectrum and Amstrad/Schneider CPC. The third one dropped the 8bit computers apart from the C64 and added th CD32 instead. Plus they were all three on the Wii Virtual Console

From what I gather, those 12.5M were only for the C64 version, and the 23M could be all versions combined, which sounds plausible to me. The C64 versions were very well loved and some of it's Killer Apps, so reaching very high sales numbers is certainly not out of the question.

RolStoppable said:

I would find it hard to believe if someone said that all C64 games combined sold 23 million copies, because the C64 was all about piracy.

While true, that actually only came later in life (it was only for the diskettes, and until 1987 3'5" diskettes were pretty expensive and copying games thus not exactly much cheaper than just buying them) and didn't concern cassettes all that much, hence why there's a steep drop in sales between TLN 2 and 3

Last edited by Bofferbrauer2 - on 20 January 2021