I got into the Pokemon series late. I was 16, and it was 2009.
Pokémon Platinum Version [ポケットモンスター プラチナ] was already out, and every single person said it was the better game. On paper, this checks out. The expanded Pokedex alone makes Platinum look far more attractive at a distance than Diamond and Pearl.
For ten years, I did not question the idea that Platinum was the only way to play the Sinnoh games. In 2019, however, I played Diamond for the first time, and realised that, as usual, I am a hopeless contrarian. Diamond and Pearl are the games I am going to play from now on, whenever I get the urge to return to Sinnoh. (which still won't be as often as Kanto, Johto, or Hoenn)
(I really should have expected this when I realised I like
Pokémon Ruby & Sapphire [ポケットモンスター ルビー・サファイア] better than
Pokémon Emerald Version [ポケットモンスター エメラルド])
Aside from
Pokémon Sun & Moon [ポケットモンスター サン・ムーン], I have always said and will always say that the evil team is the absolute worst part of any Pokemon game. Platinum expanded the Team Galactic plot, adding more of Game Freak's trademark bad dialogue. Platinum features an all-new character named Looker who appears solely to talk too much. Diamond and Pearl has roughly the same plot as Platinum, but they don't beat you over the head with it.
The worst addition Platinum made was the distortion world. It's an annoying "LOOK AT WHAT THE DS CAN DO" dungeon, placed right after the other annoying dungeon, Mt. Coronet. Diamond and Pearl thankfully don't have that, because getting lost in Mt. Coronet is bad enough.
It's not all sunshine and roses, though. The surfing speed is abysmal, and the encounter rate in caves is frustrating. I'd still take it over Platinum's shit any day.
This game did make me absolutely loathe Medicham, though.
This is different to remakes. OR/AS is not better than Emerald, for example, but Emerald is leagues better than R/S. The same goes for D/P. Sorry. I just can't play this version anymore. Why would I? But also, why didn't they just cook the games for an extra year in the first place? I mean.. Money.
Battle frontier slaps.