PC's have been in the arcade before..... 'Round 1991 I recall playing a HORRIBLE game involving a Clown of some sort. The monitor wasn't even an arcade monitor, but a VGA PC monitor. Horrible, horrible game.
Standard computer hardware has been in the arcades for a LONG TIME. There was a big multiple install of Space Wars at one college or another BEFORE Pong and Computer Space (there is a big web page out there about this somewhere). The Atari 800, Amiga, and 386 based PCs all saw arcade use, and the 486 PC platform was massively popular for countertops and quiz/card games.
I have a complete motherboard/card rack set for Tournament Solitaire and it is a 386 motherboard with a couple of custom ISA cards on it.
And my friend Dave and I both have countertop touchscreens from different companies and they are both 486 based.