There are actually four here, because two are tied for third place. These figures date from 1999. Maya has probably pulled ahead of XSI since then. I don't have firm figures for that, but that seems to be the general consensus. On January 10, 2006, Autodesk completed the acquisition of Alias/Wavefront. It's not clear yet what the implications are for the products.

By market share (units sold):

1. Autodesk Media & Entertainment (discreet) 3ds max and 3D Studio Viz combined: 44%
2. Newtek Lightwave 3D: 26%
3. Alias/Wavefront Maya and Softimage XSI: 9% each

Source: Digital Media Online

Softimage is a subsidiary of Avid Technology

Updated: 10-20-06