2015: IBM PC demoscene is beginning

Actually in the 80's I never heard people complain their machines was "single tasking". There was just a different kind of workflow those days, given the lack of Internet and other distractions. And yeah, Internet existed since 1970, but it wasn't ubiquitous or expected. A computer was a "thing" in and of itself.

As for portability, well that's the beauty of CP/M. It ran on different CPUs and environments, and provided system calls for I/O. You could run WordStar or MBASIC or whatever on all kinds of machines. There was a *lot* of software for CP/M, and quite a bit of freeware stuff. There was also a lot of source code being passed around, long before the Linux/OpenSource "revolution". People shared their BASIC programs and assembly routines (and various other languages too) for the benefit of the community. Not so much on Internet, but via magazines, printed books, and user groups. You could even mail-order floppies of freeware and source code for nominal fee.

Re: xgalaga, well it didn't build on OpenBSD when I tried a few years ago, and I don't want or care about Linux anymore. Actually I only run OpenBSD because it's the "modern" OS that disgusts me the least. I honestly wish I just kept my Amiga 500; it was a lot less trouble, and nobody had to "maintain" programs or upgrade crap all the time. It had system libraries and stuff too, but nothing as complicated as modern OS. And generally if you wanted to play a game, you just booted the floppy and there it was. Anything more complicated than that machine as a "home computer" or "personal computer" is a total disaster.
Oh and about inefficiency, even the xgalaga author finds the state of modern computers "amusing":
http://www.ibiblio.org/pub/X11/contrib/games/xgalaga-2.0.README
(and he wrote that in 1995; things got a lot worse since then...)

Anyway, Atari 2600 doesn't qualify as a home computer. It's about as close to a dedicated video game console as you can get. I'm not even sure the Famicom qualifies, seeing as how it originally didn't include keyboard, storage, or easy programming environment. The thing about home computers is that they were versatile, and they even *encouraged* the user to get in there and explore, learn, hack, and play around. Computers came with nice manuals that explained everything gently and thoroughly.