I feel inclined to tell the tale of the Japanese only green version. Yep, it really exists.
Let me explain some old history... the very first pokemon game to come out was green version. It was in Japan only, and was only available through a special mail order. That game turned out to do alright, so they decided to re-release it as blue version, with many graphics changed, as well as a few other things. blue version became a hit, so they produced red, and sent that one overseas as well, and then yellow version, because of the fans all saying that the games need to be more based off of the television show.
Now let me explain the game color code. You'll notice that in pokemon red version, (if you play it off of a GBC or GBA, but not a regular GB), you'll notice that the little guy on the screen is green, and the background is red.
In pokemon blue version, the little guy you control is red, and the background is blue.
Finally, in pokemon green version, the little guy you control is blue, and the background is green.
So while Blue was just a revamped edition of green, it did have links to it that would suggest that the games are meant to be taken separately.
Interesting, right? I have pokemon green version right here, and some of the pokemon images have them in different poses and stuff than in blue.
But I still voted Blue. Yep, good old. Blue.