Next time he comes over, show him Ruff 'n' Tumble, Lionheart, Fightin' Spirit, Mr. Nutz: Hoppin' Mad, and some other games that only came out on the Amiga! All the games you showed him came out on either the PC, Atari ST or Commodore 64 and aren't necessarily the best way to show off either the Amiga's technical capabilities, or games unique to the system.
Good to see he enjoyed it still and was impressed. How about you show him the Arte and State of the Art demos as well next time!