I think if you are talking about AAA gamer's games there is only a choice between 360 and PS3.
If you are talking about pick up and play games you have a choice between Wii and 360 with Live Arcade games.
As for sales... The Wii has the highest install base so it should sell more, but that doesn't necessarily talk about the ongoing activity of gamers in the install base. For that you have to look at the attach rate. Hence the discussion starts, because 360 has higher attach rate.
The only thing that is certain this generation is that Wii is selling and will continue to sell more hardware for the forseeable future. It is yet to be determined where each console will be by the end of the generation. This Christmas will probably determine the 2nd / 3rd place. Next Christmas will probably determine 1st / 2nd place.