What's The Best Geographical Information System?

The best geographical information system -- depends who you ask.  There is no doubt that the dominant packages in the market for almost 20 years have been the ESRI family of products, which the company itself describes under the umbrella term ArcGIS.  This includes its original ArcInfo product, as well as the relative newcomers ArcView, ArcEditor, ArcReader and various extension products.

ArcInfo has been frequently if affectionately described as user-hostile.  ArcView was develped as a friendlier but by most perspectives less powerful package.  ArcGIS is an combined interface for both of these and the other products.  ArcInfo was originally based on vector ("lines") based data, but later developed a respectable raster data format.

The GIS with next-strongest following (and sales) is MapInfo, which is very popular in local authorities.  Microlmages, SPANS and Intergraph (especially oriented towards the utlities and power company markets) are other products.  A product that was developed primarily for academics and is still quite good value for money is Idrisi.