Black and White are the best Pokemon games to date. That's why I choose new. Besides, Pokemon does not get better or worse, in my opinion, they add more Pokemon for you to enjoy.
The older ones hold more nostalgic value for me. I'm sure many of your votes were based on the same thing. The newer ones are most certainly fun, but I can't call them better. I don't think they have the same charm.
I have nothing against the new games, but the old games are what sparked the whole pokemon franchise. Plus, a few of my favorites, including dratini, vaporeon and charizard are in kanto