The obvious choice aside, we can't think of many game designers who are better qualified than Masahiro Sakurai to discuss how to make fun videogames. Which is a good job, really, because the Smash Bros. and Kirby creator has been booked by DiGRA, Japan's Digital Games Research Association, to deliver a talk on what makes games enjoyable.
Don't go getting excited, though. Sakurai's speech, entitled 'Game-ness,' will be delivered at the Fukutake Hall Running Theatre at Tokyo University's Hongo campus, and to an audience of only 150 people. If by some chance you are located near to the venue, know that DiGRA members get in free, while student non-members pay ¥500 (roughly $5) and all other non-members ¥1000 (approx $10).
We wonder what games he'll use to convey his message? Bringing up Brawl or Kirby might seem a little conceited, but those are two of the titles we would use.