Looking at the million shippers pages for Xbox 360 is interesting - Wii will probably end up 2007 similar to where Xbox 360 hardware is in the Americas right now...6-7 million. 360 has 7 million selling games off that, so I expect Wii will have around 7 as well..
Since Zelda and Wii Play are already million sellers, that leaves open 5 spaces.
Again at the least you would expect Mario Galaxy, Metroid Prime 3, and Smash Brothers Brawl.
Three down.
I think you then throw in Guitar Hero 3, and another casual game - either Wii Music, DDR, Mario Party 8, or MySims.
Everything else is to me is a 50-50 proposition or less for selling 1 million units in the Americas.
You can also look at it in terms of % of users who own the game. Why? Well Wii has 1/2 the userbase of Xbox 360, so for Wii you can look at 500,000 sellers to compare to 360 million sellers at the moment. Right now, Wii has 4 in it's entire American lifetime (w/o Wii Sports). 360 has 7. There are two ways to look at this - Wii games sell worse than 360 games (only 4 Wii games have reached the same % of Wii owners as 7 360 games). Or, Wii games are selling better than 360 games because 360 has had 3x the amount on the market (18 months vs 6 months), which would mean 360 should have 12 games to sell 1 million copies, or that Wii should only have 2 or 3 games to sell 500,000.
Regardless, by the end of the year, I expect Wii to be at 6-7 million units in the Americas, with 8-12 million sellers for Wii at 6 million units, and 10-15 million sellers at 7 million units.
Guarenteed or Nearly Guarenteed to sell 1 million units by Dec 31, 2007:
Metroid Prime 3, Mario Galaxy, Super Smash Brothers Brawl, Wii Play, Pokemon Stadium, Zelda, Wario Ware
Games that I think hit 1 million eventually, but only like 70% chance in 2007
Super Paper Mario, Rayman Raving Rabbits, Wii Playground, MySims, Guitar Hero 3, Mario & Sonic, Mario Party 8
Upto 50% of selling 1 million in 2007
Rayman 2, Harry Potter, Fight Night, Wii Music, Mario Strikers, Boogie, DDR Hot mix..