Kids play "complex games" all the time. I played Metal Gear on my NES at age 8, plenty of kids play complex games, that's not the issue.
Wonderful 101 is for kids ... the game's dev team SPECIFICALLY redid the character artwork to make it appeal more to elementary school age children.
Bayonetta 2 is a game for adults.
If they want to be successful with 5 year olds ... it's pretty easy
- Dumb down your game mechanics
- Put your games on iPhone/Android for 99 cents
- Cancel the Zelda/Metroid franchises (not kiddy enough, too complicated), focus more on Mario/Pokemon/Kirby/Yoshi games.