I tried introducing a friend of mine who heard of but never wanted to give the franchise a go for the formulaic cliched reasons (it's for little kids, blah blah), however, upon telling him that I myself still play Pokemon at my age he was 'utterly surprised'. I told him that it wasn't particularly aimed for kids and such, so he have the game a try and I loaned him my Pokemon FireRed (he was disgusted by the graphics of the old games). A few days (around 5) later, he asked me for another game. He actually loved it. I gave him Ruby, Emerald, Pearl, Platinum..finished them all, lol.
Back on the topic question, I would either give them season one of the anime or the games, like I did with my friend.