Mario Kart Wii's sales are nearly all standalone, very few are due to bundling. It's only really been bundled in 2011, and it's only sold 4.5 out of the 30 million in 2011.
It's on fast track to become the third best selling game of all time - it's only 1.4 million off. So it's looking to be in position of the following titles, among others, by the end of its life
- The best selling game of all time in Europe
- The third best selling game of all time
- The second biggest game in terms of revenue on consoles,
- Roughly the seventh best selling game in Americas if you include fully-bundled games. Either 2nd, 3rd or 4th otherwise.
- The 30th best selling game of all time in Japan
- Single handedly selling more than any racing-franchise has ever done on a single machine (like for instance the 3/4 Gran Turismo games on Ps2)
- Selling more than all the 3D Zeldas combined
- By itself selling more than all the Mario games on Gamecube did combined. Or all the ones on the GBA combined. And most likely all the ones on the N64
If you add in Mario Kart DS, the two Mario Karts this generation will have sold more than any franchise did on consoles last generation.
In other news, you should change the vote to "How much do you think Mario Kart Wii will sell lifetime?", as it's a far more interesting question. It's not completely unthinkable for it to outsellf the original Super Mario. Bros, although it is unlikely.