Though the great Diamond and Pearl are the foundation, the two year gap means extra elements and new areas to explore!
For the group that's fresh to DS Pokemon, (Diamond & Pearl) Nintendo's made sure that Platinum is the version to get. And get it you should: it may have a "kiddy" reputation, but Pokemon remains one of the deepest and most rewarding Japanese RPG games on the market, with a level of strategy and competition that's without equal.
Though the Pokemon franchise has expanded to all sorts of genres, from puzzle games to racers to photography simulations, it's the handheld role-playing game design that continues to be the true successful game design enjoyed by millions. If you haven't experienced the game, all you really need to know is that it's an RPG with turn-based battles, with players using creatures they've captured in their quest to do the fighting for them. Each of the creatures -- Pokemon, duh -- have different attributes that are stronger or weaker against others. And that's where the strategy comes into play: you need to find and utilize the best Pokemon for the situation, because you'll be encountering hundreds of battles with a huge variety of different Pokemon types. And if a friend has access to a different version, he might be able to catch creatures that are uncatchable in yours, or vice versa, so the "trading" aspect of Pokemon opens up an additional level of gameplay. It's these strategy and collection elements that make Pokemon an incredibly addictive game, and a guilty pleasure for those not in the younger skewing demographic that people assume the series is being targeted to.
For those following along, this "third game" habit has been around since pretty much the beginning of the Pokemon franchise: Pokemon Platinum is to Pokemon Diamond and Pearl, just as Pokemon Emerald is to Pokemon Ruby and Sapphire on Game Boy Advance, as Pokemon Crystal is to Pokemon Gold and Silver on Game Boy Color, and as Pokemon Yellow is to Pokemon Red and Blue on Game Boy Classic. Pokemon Version Number Three always revolves around the two earlier versions, but in the extra time it'll get subtle tweaks and enhancements without breaking completely away from the foundation (after all, the core game, creature set, and rules can't really change since it must remain a hundred percent compatible for system linking.) In other words, the creatures, attacks, and items in Platinum have to exist in Diamond and Pearl to keep things tradeable.
Ultimately, this means that if, in Pokemon Diamond and Pearl, you've poured the dozens of gameplay hours it takes to complete the adventure, it's not easy to recommend that you do it all again in Pokemon Platinum. Nintendo definitely put the effort into changing things around to make the Platinum adventure a different experience than the original release, but even with the slight change in script you'll be repeating the same stuff for, again, dozens of hours. This means you'll be visiting the same locations, talking with the same people, and performing a lot of tedious "level grinding" in order to defeat the higher end Trainers.
The Platinum adventure does change significantly at about thirty hours in. Usually spoilers are removed from reviews, but in this case the Distortion World is common knowledge: Nintendo needed to make a case for the double-dippers and openly revealed that Pokemon Platinum features a new world to explore. By the time adventurers get to the Distortion World they will have already completed nearly 80 percent of the game. Since Nintendo pretty much calls out the new area as a bulletpoint right on the box, the discovery loses a lot of the impact it could have had if Nintendo let adventurers find it without the prior knowledge of its existence.
We'll leave out the specifics of why the new area exists, but essentially the Distortion World is a extra set of puzzles that are needed to be solved before players can move onto the final gym battle. It's an area that's entirely in 3D where players will walk on the walls and ceiling, even surf up a waterfall to get from place to place. To be honest it feels a little clunky, and that can be a testament to somewhat weak visuals used in the Pokemon Diamond/Pearl/Platinum experience. It almost feels like the developers wanted to prove that Pokemon DS has been using a 3D engine all along, so it hacked up a world that goes all topsy-turvy. It does its job and creates a unique set of challenges, but it comes off a bit sloppy and low quality, especially compared to what's already available on the system. DS games have been pulling off more impressive 3D even before the original 2007 Pokemon release, and in 2009 it's even harder not to think that the visuals, both in battle and out, are dated.
The core Pokemon adventure is only a slight update to the one that already existed, but where Platinum has really improved is in its online capabilities. Pokemon Diamond and Pearl offered up battles and trades over the Nintendo Wi-Fi Connection, and Platinum expands on the capabilities. Again, the developers didn't go too far off the beaten path since the game's trying to stay as compatible with its other versions, but Platinum owners will get to do some exclusive online fun beyond what's already been in the original Pokemon DS games. Players can connect to a Platinum-only Wi-Fi Plaza and goof around with other players in a series of mini-games and community art boards (draw with Pokemon pawprints that only stick to the wall for about three seconds). Platinum owners can also take advantage of the Vs. Recorder, a new item where players can post online and save to their cartridge "videos" of their best online fights. It's not quite YouTube since all that's being saved and downloaded are tiny packets of game data, but it's still very cool to be able to see how some players handle fights between certain creatures.
And that's what really makes Pokemon so great: its little elements expand the experience even after the main game's over. If you've finished the RPG you can still hang about the town collecting the hundreds of creatures and levelling them up for use in local and online battles. Nintendo also ensures that the Pokemon investment will carry over to the console, where the player's collection can be transferred to Wii Pokemon titles like Pokemon Battle Revolution and Pokemon Ranch.
I'm reluctant to recommend Pokemon Platinum Version to anyone who's plowed through either Diamond or Pearl in its entirety. Unless, of course, you're completely addicted to the collection element and absolutely must have every creature available. However, for those who haven't jumped into the Pokemon adventure yet, Platinum is the one to back. Even though it's not a huge advancement over Diamond and Pearl, it does have a larger list of features. The single player adventure has a bit more to explore, and more importantly the online component is fleshed out a bit more compared to the 2007 releases.