As for Nikon DSLRs vs Canons DSLRs overall sales worldwide they are fairly close with maybe a lead of a few percents for Canon (both around roughly 40 percent). Nikon has made a leap the latest years in marketshare (talking about DSLRs now, not digital compacts), and Canon is not so dominant as before.
Considering the price points I am convinced that the D90 sells in much larger numbers than the 5DII. Among high end video users it might be a little different, but I remain sceptical.
