Pokemon is a strange franchise in that it's constantly leapfrogging itself. Earlier games in the series can connect to later games, allowing you to transfer pokemon you've already captured. From a player perspective, it's nice to know that all of that work getting your Gyarados up to level 50 didn't go to waste. Unfortunately, playing with leveled-up pokemon from previous games has taken a lot of the spirit out of recent releases.
Why even bother hunting for new pokemon when you've already got a squad of all-stars? This thought probably occurred to the developers of "Pokemon Black" and "White," as, for the first time in a long while, players won't be able to transfer old pokemon to the new game. At least, not until they reach a certain milestone.
"Pokemon Black" and "White" features 156 brand new pokemon to capture and collect. Like every major game in the series, your objective is to defeat pokemon trainers and become the best in the land. As you go about this task, though, there won't be any familiar faces, as you'll only be battling against those 156 new pokemon. Those will be the only ones you can capture in the wild, buy in stores or trade with friends. In fact, you won't come across a single familiar pokemon until you defeat all the gym leaders, thus completing the main game. At that point, you can explore a bonus area inhabited by old school pokemon, and transfer pokemon from previous games into "Black" and "White."
It's a shift and a bit of a risk, especially when you consider fan favorites like Pikachu won't appear until very late in the game. It begs the question, will this new roster of pokemon be as memorable as, say, the original 151? I dare you to look into the giant, adorable eyes of Minccino and ask that!
Personally, I find it kind of exciting. There's a thrill of exploration that comes with a fresh new slate of pocket monsters, as you never really know what sorts of evolutions or powers are around the corner. Of course that probably won't stop people from scouring the web for EV training shortcuts and "shiny" percentages, but for those looking for a more pure Pokemon experience, "Black" and "White" should deliver just that.