Hey there Snorris, welcome to PC! I'm Cirno and it's great to meet you~
As for what game you want, it depends on you. Just have a look at the version exclusives and other game information through Serebii/Bulbagarden/another Pokemon fansite and make a decision! You'd honestly be better off checking there than here to make a decision. It's totally up to you in the end anyway, but I personally went for HeartGold, White, and then Black 2. ^^
Anyway, moving on~! It's great to see you join up and become a member. There are a lot of members here, whether they just got back into Pokemon after a very long break or have been into it since it was released, so you'll fit in well! :3 Do you mostly only play the games, or are you into other parts of Pokemon too?
Regardless though, I hope you have a lot of fun here, and I'll see you around, all right? Feel free to contact me if you ever need any help. <3