Between BW being the best and most complete initial pair of games, B2W2 forgoing 3rd versions entirely in favor of full on sequels, something that has never been done with Pokemon since, and brilliant mechanics such as hidden abilities, not to mention all the content between games, keeps you coming back for more.
Sure it's missing some things such as the Battle Frontier, Poke Radar and Berry Farming, but it makes up for those and then some.
>Battle Frontier
Gen 5 already has 5 battle facilities scattered throughout the region, the same amount as Sinnoh and Johto's Battle Frontier.
The Battle Subway: the classic Battle Tower of Unova.
The Battle Institute: Test your Pokemon battling prowess against five trainers with ever-increasing difficulty. Can you reach Master Rank?
Pokemon World Tournament: Face off against Gym Leaders and Champions from Kanto to Unova in a nostalgic clash of the ages.
Pokestar Studios: Take part in movies with rental Pokemon and solve puzzles using the battle system. Take part in a movie with your own Pokemon and go for a strange ending, you could get a special battle animation for it.
Black Tower or White Treehollow: Take on Unova's Challenge by going through ten floors of a battle dungeon, similar to the Battle Pyramid from Hoenn, ending with a Shiny Pokemon as a reward.
>Poke Radar
Phenomena. See a blade of grass rustling, or a dust cloud in a cave? You could either find a rare Pokemon such as the Elemental Monkeys, fully evolved pseudo-legendaries such as Dragonite and Metagross, or rare items such as Gems and Evolution Stones. Alternatively you could find an Audino for a bunch of EXP, if you need it.
>Berry Farming
Join Avenue allows you to buy berries in bulk. Much better than waiting for hours, micromanaging every berry patch you planted berries in, only to barely get any berries in return.
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