The gaming website 1UP also got a chance to interview Masuda and Kawachimaru recently. Below are some excerpts from that interview.
Junichi Masuda, a member of the Pokémon design team since the first title (as well as a board director of Game Freak) who's held duties ranging from scenario director to music composer, obviously knows the game very well. When asked what he thought the major reason that people still eagerly await the release of each new title, his immediate response was its simplicity. "Pokémon games don't focus just on hardcore players; they're accessible, approachable by everyone. Anyone can pick up and play the game without feeling overwhelmed. When you focus too much attention on just the hardcore, things get complicated."
And, obviously, with its cute graphics, Saturday morning cartoon tie-ins, and watered-down narrative, the game is skewed toward a younger audience. But it remains almost as popular among adults, and the reasons for that come down to strong game design.
Source:
http://www.1up.com/do/feature?pager.offset=0&cId=3173364