ASP, I'll agree; it occupies the "PHP" slot in Win32. JSP and Mason are far less likely to be available on a given server, and JSP requires a separate server to be running in addition to the webserver (tomcat or whatever).
With the declining popularity of Apache as the frontend server, I think PHP will have this problem in the future. Eventually everything will just be a FasgCGI handler. (PHP does FastCGI just fine, but so does Python/WSGI, Ruby/Rack, Perl/Plack, etc.)
