Likely 1. Super Mario Galaxy (If Wii finishes 1st)

Likely 2. Super Smash Bros Brawl (If Wii finishes 1st)

Yes 3. Grand Theft Auto 4 (No mater what)

Maybe 4. Gran Turismo 5 (Only if PS3 greatly beats Xbox 360)

Maybe 5. Wii fit (Not sure what this will do)

Yes 6. Wii Sports (The best selling game of this generation)

Yes 7. Wii Play (Certainly)

Not likely 8. Potentially Final Fantasy Xiii (Almost no chance)

Yes 9. Guitar Hero III (Because it is on all 3 platforms)

Maybe 10. Mario Kart (It should happen if the graphics get better and Wii finishes 1st) 

Others, several DS games

gta beat halo2 of course it will beat halo 3

GTA4 is the only one that i'd say definitly... even then I'm not too sure on it. Then again I gotta wonder if a lot of casuals who bought the last one are going to buy in to basically do the same stuff they did in the last game. Steal cars, beat people up and dodge the police.

Gran Turismo has an fair chance... but i'm not sure the PS3 will have enough consoles sold.

GTA is the only game more casual than Halo. Anybody can play it. You just hop in a car and drive around listening to the radio and running people over and trying to find stars to get rid of the cops. I've seen people do it for hours.

In fact, any game that sells over 10 million has what we call "broad appeal," and if you're a bigot, you call Nintendo games with broad appeal "casual" and non-Nintendo games with broad appeal "hardcore." There are not even 10 million hardcore gamers. Anybody who still uses "hardcore" and "casual" seriously, I'd like you to tell me the best-selling game you consider "hardcore."

GTA is super casual, super accessible, and will outsell Halo 3 by a gazillion.

If you believe that Galaxy can outsell Halo 3, you're living in a fool's paradise.

Rubang B made some very good points.