Gartner recently published a report by Jim Murphy, Gene Phifer, Ray Valdes and Eric Knipp: the 2010 Magic Quadrant for Horizontal Portals.  In the report, Microsoft not only maintains its Leadership ranking but moves into the #1 position on the report – highest on both the Ability to Execute and Completeness of Vision axes – overtaking IBM.

Five vendors dominated portal selections during the latter part of 2009 and into 2010: Microsoft, IBM, Oracle, SAP and Liferay. Microsoft SharePoint is a consideration in more Gartner portal inquiries — over 70% — than any other vendor.

Source: Gartner (September 2010)

http://blogs.technet.com/b/cbortlik/archive/2010/10/19/congratulations-to-sharepoint-product-team-for-achieving-1-ranking-on-gartner-s-2010-horizontal-portals-magic-quadrant.aspx