Mario Kart - 350 hours... could easily have been triple that but I forced myself to move on.
Twilight Princess is 2nd at 220 hours
RE4-Wii edition is 3rd at 205 hours
Endless ocean 2 4th at 199 hours
The Conduit is 5th at 155 hours
Got 3 more games I have spent over 100h on, and another 8 with more than 50 hours.