Pokemon Platinum expands the already awsomness of D/P by ways you wound't imagine from past games like crystal.
Pokemon Platinum is the best expansion game becuase they did change minor things and major things like new pokemon, new gyms, updated citys, updated story line, better post game like the new and improved battle fronteir from emerald, and new girantina
Pokemon Platinum was thought to be another useless expanson game like yellow or crystal that didn't change much just becuase Pokemon Diamond and Pokemon pearl were loved by many people and was verey successful. Pokemon Platinum proved way better than it's prodecsers and also poked out alot of D/P's flaws, like lame settings.
This is not a yellow or crystal, so buy away pokemasters!