SP1 is a prerequisite for installing SP2. (W2k8 released with SP1 included. Vista SP1 information and downloads @ Windows Vista SP1 TechNet
W2k8SP2 and Vista SP2 – Five Language Standalone version can be installed on systems with any of the following language versions: English, French, German, Japanese, or Spanish.
If your system has additional languages use the All Language Standalone to install SP2.
Windows Server SP2/Windows Vista SP2 page on TechNet/MSDN for additional details and documentation.