This was me four years ago. Back then, I have not played the fourth and fifth generation and when I got back into Pokemon, sixth generation came out and I played that after playing third generation. Seventh generation came out after and I played that after playing sixth generation. After playing the seventh generation, I ordered fifth generation online since I did not play that when it came out and is not being sold in stores anymore. You don't need to play a game in order in the year it first came out. Just pick a Pokemon game that appeals to you the most.