I'd say one should be Pokemon Snap. It was originally a N64 game, but is also available on Virtual Console, so would probably be the easiest to access. Other than that, I'd rather see Cohh play one of the Classics, something like Gold, Silver or Crystal. They'd have to be played via emulator though, as I'm not sure anyone has ever bothered come up with a capture method for the OG Gameboy.
Pokemon Gold/Silver are the best and largest pokemon games! But I suggest playing the Soul Silver or Heart Gold remakes. Same amount of content but with more modern and updated game mechanics. Main I would suggest Soul Silver. ^^
Since the new Pokemon games are being released soon, I think one of those would be fun to watch! But if we're talking the older ones, I'd say I have the biggest attachment to red/blue/yellow versions. If you're wanting a newer style, I thought X and Y were a lot of fun!