Xbox is well ahead of Cube in the US... 1,1 million in fact. From the NPD report:
December Hardware Sales:
PS2: 2,733,000 (+ 107% over November)
XBOX: 1,033,000 (121+%)
GCN: 619,000 (+32%)
GBA: 2,215,000
Cumulative Installed Base:
PS2: 15,870,000
XBOX: 4,601,000
GCN: 3,583,000
GBA: 11,894,000
In Europe some press says Xbox has sold 1,8 million. Anyway it's pretty 50/50 here, so it doesn't matter who has the small lead. I'd say Cube is ahead in worldwide numbers for now but even that isn't much of a lead (at most about 800k units). Just to set it straight.