I didn't read the whole discussion but about the OS'es...
In 1981 PC-DOS was released (same as MS-DOS 1.0) and Amiga wasn't even in the plans back then.
1981 CBM Inc (leaded by the marketing master mind Jack Tramiel back then.) had just launched VIC-20 and VIC-1540 Floppy Drive that used CBM-Dos 2.0 (version number?) and it was 100% comparable to PC-DOS 1.0 (afaik, original PC-DOS didn't supported even sub-directories and why should it? 320 KB floppies never got past the file entry limit. (512 entries.)
PC-DOS 2.0 (1983) the sub directory support as well as support for 10 MB Hard Drives. at the same time, Tramiel launched C64 and 1541 Floppy Drive that had only slight modifications for older brother. Still, C64 had so HUGE influence that it made Microsoft notice that they were losing home / small computer market totally And so MSX (MicroSoft eXtensions) consortium was founded. in this case, MS was the ppl defining software side of computer and several manufacturers licensed the technology and used it. Still MSX didn't make very well outside the japan, where the major makers were coming.
In 1984 Jack Tramiel was basically smoked out from his own company and after that CBM Inc never got strong enough CEO, to steer the company in the success they had with VIC-20 and C64. Jack Tramiel got himself in the ATARI and after CeBit 1984 where small Amiga Inc has showed a running prototype of upcoming system, he smelled the money. By making huge public money offer buying the whole Amiga Inc, He also woke up The Commodore. Started terrifying offer competition which eventually ended to Commodore winning with price that has been later said to be more than 6 times of reasonable price of Amiga Inc. Still Tramiel has losed the battle, but he still had advantage, because their own ST-series were more further than Amiga's design. As a marketing guy, actually bought quite lot more living time to dying company with quick launch of ST series before Commodore got Amigas up and running. when Amiga 500 and Atari ST were competing of the 1st place, the competition was really hard and eventually killed the ATARI off. Still, the end of Commodore looked like glorious, but fact is that they sold most of the time Amiga series with very thin profits and weak CEOs in the lead didn't make things any easier. Most likely, Commodore hardly got any use of buying Amiga Inc, because price wars cutted the profits so weak. In the April 1994, CBM Inc was declared to bankcrupt in the Bahamas. though Amiga rights were sold, still this basically ment end for Amigas as well.
While all that happened, also lot happened at PC side too. almost at the same time with AmigaOS and WorkBench releases, Microsoft and IBM showed OS/2 operating system, that had all what AMiga had plus much more. Before OS/2 MS/PC-DOS 3.0 and MS/PC-DOS 4.0 were released and hardware had gone forward from 8086 to 80286. difference between Commodore path and IBM path is that PCs were all backwards compatible, CBMs weren't. also, PC side was pretty much steady, while ATARI and Amiga were having real cut throat competition and you could have picked wrong system.
and then about the Doom... Fact is that there's no way make it run with basic Amiga 500 with playable frame rates. when doom was released in 1994, majority of Amiga systems were 500 / 600 machines and only minority had 1200 with AGA chipset. Basically, there just wasn't market for it anymore. IF JC would have ported Doom to Amiga, it would more like speed up the death instead of slowing it down.
Bluebyte's The Settlers was the last real big hit for Amiga that made PC-players really jeallous, just because there wasn't PC-port. But when the PC-port at last 9 months later came out, tables turned. with _old_ 386 and 4MB memory, The Serf City (as it was called in PC) run a lot more faster than hard coded Amiga port on A500 with 512KB memory expansion. that was a last straw for many amiga users strugling about updating their A500 to faster Amiga or perhaps jumping to PC-world. (all this from my nordic point of view.)
There's so many IFs. what would happend, IF Tramiel would have won the offer competition and Amiga has become a ATARI? and what would happened if Commodore wouldn't smoked Tramiel out and their CBM 9000 with MC68000 and System V based OS would have taken the market? it was obiously originally targetted against IBM and Microsoft...
but oh well, past is a past... In any case, there's whole bunch of mighty machines in the history and they all have affected on the way or other to development of the industry. Enjoy them whenever you have the possibility.
wheeh... there's for start...