Playing the games Chronologically is really good too
Red, Blue, Yellow > Gold, Silver, Crystal (HG/SS *If you prefer* > Ruby, Sapphire, Emerald > Diamond, Pearl, Platinum > Black, White, Black 2, White 2.
I would say go for HG/SS, D/P/P and BW, BW2.
Those are really good games.
Or if you like Nostalgia, go with RBY, GSC (FR/LG)