Red/Blue/Yellow for me... but thats mostly because I'm an oldie and thats the series of Pokemon that I grew up on
(to get an idea of how much of an oldie I am when it comes to Pokemon, you must understand that I was getting the card game
before they ever came close to the Western market. I had the bloody things imported by my Japanese grandmother! I used to know the name of every 151 Pokemon [in Japanese, naturally], and remember a time when the abbreviation "Pokemon" didn't exist, and they were called "Pocket Monsters". Ah, good times... I don't go close to the stuff now, and gave away my rather large collection ages ago)