Relative increase, or increase in solid numbers?
If relative, I guess GTA III (as previously mentioned) takes the victory. (With 1M+ sales originally only)
If in solid numbers, it's Mario Kart Wii if you include the Wii.
If you don't include Wii, but include DS, it is probably Mario Kart DS, as it should sell more and slightly outedge how much GTA III beat GTA II with.
Edit: Nevermind! I found the winner.
Tetris on NES: 5.58M
Tetris on GB: 30.26M