Combining single player games with some community aspects might be a cool way too. Think of the messages in Souls, or ghost data of other players in racers or Rayman. And MIiverse (*sigh*) posts displayed in Splatoon and Smash. That way the games are still single player, but use Internet to enrich the experience.
User generated content: I think of Mario Maker. The ability to create levels or other game data (Minecraft-creations for instance) and share with the community is very welcome.







