ArcGIS Explorer is a free downloadable application that offers an easy way to access online GIS content and capabilities. With ArcGIS Explorer, you can connect to a variety of free, ready-to-use datasets hosted by ESRI. Combine these with your own local data or other 2D and 3D Web services to create custom maps and perform spatial analysis (www.esri.com).
With ArcGIS Explorer, you can
* Fuse your local data with data and services from ArcGIS Server, ArcIMS, and Open Geospatial Consortium WMS to create custom maps.
* Perform GIS analysis (e.g., visibility, modeling, proximity search).
* Use custom tasks to manage, edit, and analyze your data.
* Share your maps and results with others.
ArcGIS Explorer has capability to open many types (sources) of file such as data from server, geodatabase, shapefile, and raster data. It also supports KML file.
I think it can be one of GoogleEarth alternatives.
Download and try free ArcGIS Explorer http://resources.esri.com/arcgisexplorer/index.cfm?fa=download