Currently Online 
Sony just said that GT Sport is for ages 7-77, so there is that.
Other than that, depends entirely on what kind of games you want to play.
Wii U wins with platformers and kids will probably love Mario Kart. It also has free online if you're not into online games but still want the option to play now and then.
PS4 wins with fighters and they seem to have some great downloadable games coming. They win with niche Japanese games and RPGs, as well. They have the most variety when it comes to exclusives. Online is behind a paywall but PS+ is a pretty darn good value.
Microsoft has the big exclusive shooter franchises with Halo and Gears. Their online service is probably a good value, as well, but I don't know enough about it to make that claim.
