I'd have him play me in Smash Brothers.. as he'd still be just as good as he was.. after that, I'd have him play me in Tony Hawk ... after he accepted I'd be amazed.. if he didn't accept.. I think he would be starting to remember.
After beating him a few times, I'd see if that helped.. if not.. I guess I'd become his best friend again... the friendship has a lot of deep meaning with games.. we can talk about it for hours and not really go in any depth at all.. I'm sure it would happen again. It would suck, but I'd do my best. Oh, and I'd also state my name and all that.. if they didn't know they knew me.. they might feel weird about some guy bringing his cube in and say.. "Lets Play.. .... yeah yeah, you know how, trust me."