My point is that C's popularity quickly outgrew the popularity of UNIX, especially during most of the 1990s before Linux made UNIX accessible to us "PC peasants". Most 1990s PC games were written in C, and C was also the dominant high level language on 16/32 bitters like the Amiga or Atari ST.
(and note how I specifically wrote "dominant high level language", not "dominant language", since assembly coding was indeed very relevant on those machines, for UI apps 100% assembly was quite rare though, and hybrid C/ASM seems to have been more common).
It depends: for the classic 8 bit home computers, games were mostly written in assembly. Later DOS games were commonly either written in Pascal or C, but quite a bit off Assembler code was often used for the more performance-critical code sections.