On one of my arcade cabinets, I have it running on an old P4 with a GeForce FX 6200. You wanna talk old and outdated, there ya go. But still, it runs much much better then a Raspberry Pi. Now, you wouldn't think something that old would have much muscle, but you'd actually be pretty surprised to find out what an old GPU like that can do in even modern games. You wanna talk emulation, well MAME for it is nothing, haven't tested it on any harder to run emulators yet but I'm guessing results should be quite good. Mame system requirements have went up over the years sure, but like others said, it depends on the platform, and even with say Mame, what doesn't run on it is a much smaller number then what will. So with that being said, your best bet is look at the platform, or even specific game that is concerning and figuring out from there if what you have will work for you.