Get Pokemon Black or Pokemon White.
I just can't really seem to go backwards and lose all the wonderful features that were in Gen V, like UNLIMITED USE TMs.
Also, there's none of the HM garbage - you only have to use an HM once in the game, and it's pretty early on - meaning you can actually train six Pokemon and not have to sacrifice a space in your party for an HM user.
The EXP formula has also been reworked - now you get more experience if you beat a higher level with a lower level Pokemon, which makes it easier to train six Pokemon because you'll gain more EXP than if you trained only one or two.
On the flip side, the Fire and Grass starters are pretty worthless in BW... but there are plenty of great Pokemon that I believe more than make up for it.