According to this Wikipedia entry , "It was re-released in 2008 as Ghost in the Shell 2.0 with new audio and updated 3D computer graphics in certain scenes." It sounds to me like it's the same movie with a few graphics tweaks, a remastering of the original rather than a remake.
On the Ghost in the Shell wiki (there just had to be one) :
Ghost in the Shell 2.0 (GHOST IN THE SHELL／攻殻機動隊 2.0, Gōsuto In Za Sheru/Kōkaku Kidōtai 2.0?) is a reproduced version of its original 1995 counterpart. It was produced in celebration for the release of The Sky Crawlers in 2008. For the films Version 2.0 release, all the original animations were re-produced with latest digital film and animation technologies, such as 3D-CGI. The original soundtrack was also re-organized and re-recorded.
So, it's the same movie with updated graphics and audio.