Sounds like you've just discovered this... that's cool. Keep a personal archive of as many roms as you can, before the internet apocalypse arrives. Emulation on PC has been around since the DOS days... one notable DOS emulator was ZSNES, which could run roms reasonably well even on a 486/DX2-66 (accuracy is sacrificed of course).
Just installing Retroarch and loading a rom is nice and all, but there are ways you can ante up the experience. One of them is to run your emulators on a CRT display at each console's native resolution. This can be accomplished with certain ATI video cards and a CRT/TV that accepts RGB or SCART input. I've made a post about it a few months back describing the setup, . You can use a production/broadcast video monitor (PVM/BVM) which usually have RGB inputs, a TV with a SCART input (rare in North America), or do what I did and modify a TV set to accept RGB.
(post is archived)