Ruby, Sapphire or Emerald will be a good Gameboy game for you to play. Since you played Gen 1 and 2 already, It would only be right to start with Gen 3 :D
As for Black & White; Yeah, it does get a LOT of hate, and I don't know why.
The pixels in the battle screen? The originality? (LOL REALLY?) The Storyline?
/startrant (skip if you want)
I assume it's because of the originality, which I find hilariously stupid.
Seriously guys. You think BW is unoriginal? How about you take one good look at Voltorb... or Zubat.
Really.. a Pokeball upside down? A strangely-colored bat? That's original, but the exotic Pokemon on BW ISN'T?
...and don't even tell me about Beartic or Vanilluxe. Ursaring took the spotlight before Beartic.. and idk about Vanilluxe.
...but ANYWAY, Black and White is a fantastic game. If you're keen on Pokemon games though, you should probably start with Emerald or Platinum beforehand. Just so you can experience it all