The only thing that makes Diamond and Pearl better than Platinum is that you fight Fantina after fighting Maylene and Wake, not before. I'd prefer it if in pokemon Platinum, you fight her after those two.

This is because when I played pokemon Diamond when i was a kid, I like how long it took for me to get to the third gym leader after beating the second gym leader. You have to go from Eterna city all the way to Veilstone city passing through Oreburgh city, Hearthome city and Solaceon town and I liked that. Pokemon should have more places to stop by inbetween gym leaders.