My current pc (which is from 2012, i3 3220, r7 250), runs ps2, gamecube, wii and everything older than that. Start with things like super mario 64, conkers bad fur day, crashbandicoot if you like platformers. The reason to run emulated games is to play non pc titles. Hope this helped.
Mostly people emulate the consoles of their childhood and play all the games they used to play back then.
Anything else doesn't make sense,if you want to play a new console title you can rent a console and the game from a video store and play it,the pS3 was even able to run games form ps1 and ps2.
I use a bit of dosbox to play dos games bought from gog on my pc. I also run dos games and nes games emulated on a nintendo ds. The ds can also run dos based windows versions using a dos emulator and linux. I have had ds linux and windows 3.0 working on a dsi. A raspberry pi for like $10 can be used to emulate most 80s and early 90s platforms, as well as run linux games.