>>50191704People don't seem to understand, the entire point of platinum, HGSS, emerald, etc. is the (near) infinite postgame. There's always something to work towards in the singleplayer, for the newer games you just get your battle tower clone except with all the challenge removed, and then the next game/expansion will just be "catch all the legendaries lol".
There's not really anything in the way of additional side activities like contests etc, theres no interesting twists on battles like you get in the Battle Frontier, there's just nothing.
The actual main playthrough up until beating the elite four is only like, 1% of the actual pokemon experience, everything after that is what leaves the main impression.