Lets be realistic based on past sales, hype, mass market appeal, installed base and etc.

will beat hands down 

1. Super Mario Galaxy

2. Super Smash Bros, Melee

3. Grand Theft Auto 4

4. Gran Turismo

5. Wii fit

6. Wii sports/Wii play

7. Potentially Final Fantasy Xiii if it matches the sales of Final Fantasy Vii 

Brawl, not Melee (but you knew that)

I would add Mario Kart Wii to that, based on the success of Mario Kart DS.

Guitar Hero III if you count all platform sales.

Yeah mario kart has a much better chance than even Galaxy does.

I think Halo 3 should end up roughly the same as, or 1 million more than Halo 2..... so it will be under 10 million.
Gran Turismo is certainly possible, but it will be tough.
GTA4 is a certainty (assuming you are counting both 260 and PS3)
Wii Fit i am not sure on, but if it can perform week in week out like brain training then definately.
Wii play is a definate.
I would doubt FF13, but it could suprise me.

HALO 4

Possibly Rayman.

We have to be a little realistic guys, Galaxy won't, Brawl is looking to be amazing and has incredible hype, but unlikely to surpass Halo.

Really I think the only one with a shot at it is Grand Theft Auto, and we are talkin one system not multi system.

.... if we are going that way 1080

Ninja Bread Man 2

Galaxy will. Nintendo games arnt known to be front loaded but have incredible legs. Look at Pokemon,Brain age and Nintendogs on the DS. Galaxy will be floating in the top 50 for the next 3 years