Is there an order to the Pokemon games chronologically?

As usual, Bulbapedia holds the answer:

(Fire) Red, (Leaf) Green, Blue and Yellow, as well as (Omega) Ruby, (Alpha) Sapphire and Emerald, are all simultaneous.

Three years later, (Heart) Gold, (Soul) Silver and Crystal, as well as Pearl, Diamond and Platinum happen.

Some time later, the events of Black and White transpire, and two years later, Black 2 and White 2 happen, contemporaneously to X and Y.