I have a MiSTer FPGA system. I set it up but I haven't really used it yet apart from testing. I should set some time aside one day to go through and play some games on it. Something that I will never play in person because it will cost $1,000 to buy it, like Koei Flying Squadron
It was pretty easy to put together and set up following the guide on the Classic Gaming Quarterly website. The only thing I didn't get working yet was Neo Geo, but I haven't put that much effort into getting it working yet.