The performances of the gaming market say otherwise as both NES and SMS chipped away at the computer market to the point that the SNES and Genesis outright ended that era until PCs took over, cassette games were dirt cheap but non of those games were anything like SMB, Sonic etc... which consoles were being driven by it was a complete shift in the market that ended with the likes of the old guard going under as they couldn't compete with the new consoles. To give you an example the Amstrad CPC sold 3m compared to the 6m of SMS and 8m of the NES highlighting my point as consoles at the time of the release of these devices were dead yet the home computers were beaten out in the end.
Just to make it clear, it wasn't the SNES and Genesis Megadrive! that killed the other computers, the PC itself did. Intel kept pushing the X86 further and further and after IBM stopped caring, other companies started to create their own graphics cards. Both ensured that no competitor in the computer market could keep up with the PC. Commodore went under, Atari tried to realign itself onto consoles with the "success" we know. Apple became a niche product for graphics and audio later on, but during the late 80's and early 90's, they actively tried to get computer gaming on the MacIntosh going strong like it did early on the Apple ][, but never got that known for that domain. However, none of this was the console's doing.
I gave the Amstrad as an example of computers other than PC or Apple of the time. But hey, 14M consoles sold better than 3M Amstrad, so consoles killed computer gaming, yay. Sorry, but that's patently false. Since you added up those two consoles (and I'll round it up to 15M with PC Engine and Atari 7800 sales), I'll do a similar thing with computers, with their sales during the lifetime of the third Gen, so 1985 to 1994, cutting off the sales before 1985:
Atari ST: 2M
Apple ][: 3M
Granted, those numbers are worldwide numbers, but only Apple computers and PC really were popular in the US. A part of those computers were used for professional reasons, especially with the MacIntosh and the PC. But if even just 10% of the PCs were used for gaming in Europe, which is a realistic number since Europe was the main PC market at the time, then those alone outsold the 3rd Gen consoles of the same timeframe.
The Nintendo eShop rating Thread: http://gamrconnect.vgchartz.com/thread.php?id=237454