Halo on Wii is virtually impossible for fundamental reasons:
Halo is Xbox's flagship IP. Porting to competitor hardware contradicts 20+ years of platform strategy. Only Halo on Nintendo: Halo: Combat Evolved GBA prototype (cancelled), Halo DS pitch (cancelled).
For Wii FPS: Metroid Prime Trilogy, Call of Duty: WaW/BO, The Conduit, GoldenEye 007.