Now I know there's enough of these threads.. probably bust I'll make one. So here it goes. The PS2 data is from Video Game Sales Wiki. Wii sales are from Nintendo. I'll do by the end of each fiscal year. Also I believe PS2 1st FY ending was Japan only.
1st FY PS2- (1.41) 1.41 Wii- (5.84) 5.84
2nd FY PS2- (9.20) 10.61 Wii- (18.61) 24.45
3rd FY PS2- (18.07) 28.68 Wii- (25.54) 50.39
4th FY PS2- (22.52) 51.20 Wii- (20.54) 70.93
5th FY PS2- (20.10) 71.30 Wii- (15.08) 86.01
6th FY PS2- (16.17) 87.47 Wii- (9.84) 95.85
7th FY PS2- (16.22) 103.69 Wii- (3.99) 99.84
8th FY PS2- (14.20) 117.89 Wii- (1.22) 101.06
Wii fell behind PS2 by having terrible legs. PS2 went to sell 155m units while Wii probably won't even hit 102m.
bet with toastboy: I win if Wii U is still in 2nd place by the end of the year. He wins if Xbox One is in 2nd place by the end of the year.