Bolt the Cat
Bringing the Thunder
Emerald was different because it had a different feeling than R/S. Platinum, however, didn't; it looked exactly like the same game (history wise). You play Platinum the same way you play D/P, something it did not happened with B2/W2.
I'd like to know what you consider to be a "different feeling", because I'm struggling to find anything that would make Emerald a more different experience than Platinum. Both were basically the same game with a slightly different storyline, but Platinum also had an improved regional dex which changed the kind of Pokemon you would encounter within the main game. What did Emerald have that surpassed that?