It's still far too early to crown anyone as the champion and winner of this generation. This isn't a "sprint" and you never know if the PS3 will take off in 2008 and close the gap quickly. If you compare the PS3's sales at 5 months of release and that of the 360, how do the numbers compare? If I looked at it correctly, the PS3 is above the 360's numbers at this point in its life.
Later this year you should see the PS3 begin to get better numbers and close the gap between it and Xbox by quite a bit. I do have a 360, but Halo 3 isn't a game that interests me. Halo 2 disappointed me greatly and I wished I had never bought that game as I traded it in a couple weeks after buying it.
The Wii will continue to have very good numbers through this year and even into 2008. However, I think that is when things will begin to stagnate (If not sooner) as gamers will see some very impressive games come out on the PS3 and even the Xbox that the Wii just cannot physically handle.
I am not saying that the PS3 will win it all, but it will be very very strong this generation and give the Wii a run for it's money and soundly beat the 360. The thing that could hurt the Wii is that it may not have near the life cycle that the PS3 will have because it's much more advanced internally than the Wii.
I remember when I bought my PS2 at launch and the games were just horrible. Now, look at Gods of War 2 for an example of how games improve over the life cycle of a system. When the programmers learn the best way to program the games to get every bit of power out of a machine and make it look amazing and play amazing.