there's a very small and niche crowd that still plays MAME fighting games with MAME32k (through kaillera). Old, has syncing issues sometimes, need servers nearby, but when it works it's pretty fun. :)
There are some people that play 64 games on those same servers iirc. I think they used mupen + kaillera. I tried it a few times and the syncing issues were a drag (had to restart everything to resync), but with the mame thing you can discover servers near you and see what games are being hosted/played as well as the emulators and their versions.
edit: if anyone's interested, 0.64 was the popular version for classic fighting games.