The 2gb limit is a Microsoft limit... in fact, you have 2gb for application and 2 gb for the OS... you can push the limit to 3gb if you edit manually your boot.ini in xp or edit your register key in Vista...
PAE will change nothing if you remain with a low end Windows version... by example, Windows Vista starter and Windows 7 starter have a limit of 1 gb address memory in place of the 4 gb expected for a 32 bits OS... but a good old 32 bits version of windows 2000 datacenter have a limit of 32gb...
Game devs, when they make their code, choose the OS that the majority of people have because they need to sell, they are a business after all...