Pokémon Red and Blue arrived September 30th, 1998. It was one of the best selling Gameboy games of it's time. Overall, Pokémon Red and Blue sold a little over 20 million copies worldwide. Keep in mind, this was before the digital age of iPhones, Kindles, and Tablets that we live in now. A Gameboy with a copy of Red and Blue was the coolest thing in your pocket back in 1998 and the millions of copies out there showed that.
Fast forward to 2010, almost a complete 12 years later and in less then 30 days Pokémon Black/White will be arriving in Japan (March 2011 for North America). Besides the TV Shows, Movies, Toys, Trading Card Games, Pokémon is one of Nintendo's best selling franchises in today's game market. Out of the top selling video games (source) this year, HeartGold falls in the number 7 spot and SoulSilver ranked up to the number 2 spot. That's pretty impressive, eh?
More importantly out of all that, you probably want to know why you need to start playing? Here you go: