Who is the most popular Pokemon in Japan?
http://www.nintendoworldreport.com/news/24410
In September, The Pokemon Company announced that they would be hosting a poll so players in Japan could vote for their favorite Pokemon prior to the release of Pokemon Black and White. The winning Pokemon would be hailed as the most popular, and players would be able to download it free via Black and White's Dream World features.
The winning Pokemon was Arceus, a legendary Pokemon first introduced in Diamond and Pearl. Following it was Darkrai, also from the fourth installment of the Pokemon franchise. In third place was Deoxys, the shape shifting legendary Pokemon introduced in Ruby and Pearl. A movie called "Destiny Deoxys" featured the character as one of the main Pokemon.
Series mascot Pikachu landed in fourth place, while Meowth closed the top five. Both characters have been used extensively in media, from cartoons and comics, to spin-off games and tech demo demonstrations. Both are also from the first game in the series, Pokemon Red and Blue.