Diamond, Pearl, Platinum
#387 (Turtwig) - #493 (Arceus)
Roark, Gardenia, Maylene, Crasher Wake, Fantina, Byron, Candice, Volkner
Elite 4 & Champion:
Aaron, Bertha, Flint, Lucian, Cynthia
Rotom, Uxie, Mesprit, Azelf, Dialga, Palkia, Heatran, Regigigas, Giratina, Cresselia, Phione, Manaphy, Darkrai, Shaymin, Arceus
Generation IV was all about myths and legends. It brought with it some of the strongest legendary Pokémon-related plots yet, along with the biggest cast of said Pokémon. In Diamond/Pearl/Platinum, the new Sinnoh region was the setting that housed the three legendary creator Pokémon: Dialga, Palkia and Giratina. Outclassing all of them, however, and one of the most popular legendaries of the series, is the god Pokémon, Arceus: the divine creator of the Pokémon world. Quite the epic setting, eh?
Including the plethora of new legendaries, another 107 Pokémon were introduced. If you've been keeping count along the way, that's 493 now. As usual, over 100 new moves were added along with new specialty pokeball types, 47 new abilities, and the return of the day/night mechanic.
Perhaps the standout addition to this generation is splitting moves into physical and special categories. Physical moves are those like tackle, crunch, quick attack and cross-chop, while special are those such as razor leaf, hydro pump and psychic. By dividing moves into these categories, a whole new level was added not just to the main game, but to the competitive metagame as well. With this addition, certain Pokémon that were adept with all their moves in the past may find their specialty in one type or the other based on their attack and special attack stats.
Many upgrades made overall improvements to the series, including brand new 3D graphics, visible differences between some male and female species, Pokémon and gym leader animations (in Platinum), and improvements to many events. The Pokémon Contest and Battle Tower made a return, along with new categories and other minor improvements. In Diamond/Pearl/Platinum, you could even create your own secret base underground to go digging for items and play games with your friends. Which, of course, leads me to my next point...
Proper online battling and trading with Wi-Fi! It had been a long time coming, but Gen IV finally allowed you to trade and battle with other trainers from all around the world. The Global Station was introduced where you could find trainers to fight, put your own Pokémon up for trade, or find a Pokémon you wanted from someone else. The system was (and still is) a little clunky, but allowing players to interact with trainers from across the world really brought a new dimension to the series.
Of course, alongside these new games were the remakes of the two most popular games in the franchise: Gold and Silver. Reborn as HeartGold and SoulSilver, these two versions took the franchise to a whole new level. And, no, I'm not just biased because they're my favourite... probably. With beautiful updated graphics, the return to Johto was one to remember. Interestingly, HeartGold and SoulSilver brought with them something not seen since Yellow back in Gen I: allowing a Pokémon to follow you outside battle. This time around, it could be any of the 493 Pokémon and not just Pikachu. Awesome, right?
You know what my favourite addition to this generation was though? You could finally run while inside a building. Hallelujah.
The ability to have Pokémon walk behind you in HeartGold/SoulSilver was a most welcome throwback to my childhood days spent playing Pokémon Yellow. Having a "special" companion accompany you as you explored Johto helped reinforce the idea of forging a bond between Pokémon and master. That idea was taken even further with the introduction of the Pokéwalker, which eased the drudgery of many a workday as I took a beloved Pokémon on my real-life commute.
In Generation II, berry trees were first introduced. Though perhaps not as interesting as other innovations, I religiously watered and harvested my berries every single day. I never really used them often, and they just sat in my backpack, but it was a fun little addition nonetheless. You can imagine how excited I was when over 60 new berries were added by Generation IV.