What should be the first Wii game that I buy?

I'm a first person shooter kind of guy and I just absolutely love Call of Duty 4: Modern Warfare: Reflex by Trey Arch. It's about $50 and it has an okay campaign (single player) mode and an awesome online multi-player mode with many different game types from planting bombs and capturing flags to just plain and simple team death-match. On top of that, the maps are great and the leveling system is awesome because as you level up, you can get more weapons and perks. There are many challenges to do, there's even a challenge in the "Elite" category called "What ?" where you have to shoot through a wall and explode a barrel to kill somebody.