Just like Kevan, Hikari, & Keropla mentioned above me. Black2/White2 have been my favorites so far. Black2 took me out of emulation and buying the actual DS games and DS consoles.
Unova has been my favorite region so far, all my favorite Pokemon can be found in B2W2, my favorite places in the Pokemon World are in Unova.
Now, in both games, I'm in the post game, and there are still places I have not yet explored, having such a fun time exploring.