Medieval: Total War II is a great strategy game. It's a good idea to keep it along with Mario Kart.
Sell the rest (you can sell Total War II as well once you've played it); don't ever sell Mario Kart.
I recommend to buy Little King's Story and/or Muramasa: The Demon Blade.
Also: You loved Wind Waker, so quick, go buy Phantom Hourglass and/or Spirit Tracks.