I've had the occasional TiVo customer call in and inquire about the games accessible on the TiVo. They seem to be more popular than I was expecting, and more than once I've heard a customer opine about the selection of games. Meaning they wanted more. In general, the more frequent TiVo game users appear to be either age-advanced or elderly, predating even the Atari or Calecovision generation!
So I thought I'd suggest something along the lines of simple multiplayer games. Like a few different card games. Something relatively simple where the rules are already commonly understood. I believe it would get quite a bit of use!