There are 5 Generations of Pokemon:
Generation 1: 1996-1998
Mainline Games: Red, Green, Blue and Yellow
Main Platform: GB
Generation 2: 1999-2001
Mainline Games: Gold, Silver and Crystal
Main Platform: GB/C
Generation 3: 2002-2005
Main Platform: GBA
Mainline Games: Ruby, Sapphire, Emerald, Leaf Green and Fire Red (last 2 remakes of 1st gen)
Generation 4: 2006-2009
Main Platform: DS
Mainline Games: Diamond, Pearl, Platinum, Heart Gold and Soul Silver (last 2 remakes of 2nd gen)
Generation 5: 2010-
Main Platform: DS
Mainline Games: Black and White
The original games are Green and Red. Blue was a revised special edition of the 1st two games. However when the game was brought to the West, green was removed and replaced with Blue. So we got Red and Blue, instead of Red and Green. Which is good as we avoided this fugly mew sprite:
