Dice Poker in The Witcher possibly took more time than the game itself, at least in Chapter 2. It basically is what I did when I had nothing else to do, and in Chapter 2, there's the possibility you may have large chunks of nothing to do.
In Twilight Princess, I spent an insane amount of time doing the various mini-games and fishing. Not sure if it ever accounted for more than the rest of the game, but it did a take a good chunk of the game.