Simply unzipping the update site into the Eclipse installation is not sufficient. The plug-ins have to be installed. To install the Platform EGO plug-in, start Eclipse and then do the following:
From the Help menu, select Software Updates, and then Find and Install.
In the Install/Update dialog box, click Search for new features to install. Click Next.
In the Install dialog box, click New Archive Site.
Navigate to the downloaded Platform EGO plug-in location, click OK and then Finish.