Galaxy will end up with the better sales at the end of their respective lifetimes. Both games are going to sell ridiculously well, of course, so I'm not sure how much that matters. Galaxy won't pass Halo 3 until late in 2008 at the earliest, and probably not until 2009. I say this because as we move further into this generation, the Wii's install base lead is going to grow larger and larger over the 360. The two consoles are essentially even right now, but by the end of 2008 the Wii should have a lead of more than 10m consoles. (I'm estimating that we'll see something along the line of 42m Wiis and 25m 360s by the end of next year. That's a huge disparity, and it will only grow larger in 2009.) Even though Halo will always have a higher attach rate, the sheer number of Wiis out there will result in more people picking up a copy of Galaxy.
But I'm really more interested in continuing the argument between "who" and "whom". 
End of 2008 totals: Wii 42m, 360 24m, PS3 18.5m (made Jan. 4, 2008)
