>>44379467BW1 are my favorites from gen 5, most people like 2 the best though. there is a lack of pre gen 5 pokemon in Bw1 for the entire main game, and after you beat the story which is a bit more elaborated than all other older entries, you can finally see pokemon from older gens. The giant chasm is great for training, however audino training is tedious and boring imo. I don't like the new xp system, personally. Other positives are hidden abilities (sadly dead since dream world was shut down, but there are still some pokemon with them in hidden grottoes in BW2), you can't pass your items from older gens to them, poketransfer is a nightmare, battle subway is great in general, and you can exchange rare items during certain days of the week. Also fan made GTS is still working for all gen 4/5 games, if you can connect to it. White forest or black city, offer either more wild pokemon or more evolutions. Also musicals which most don't care about.
BW2 are the best for most people, and they have some new features like hidden grottoes, the avenue, movies and new gym leaders that weren't in BW1. The story is the continuation of Bw1, so it is recommended to play those first. They mix some pokemon from older gens in the main story, everything is usable as well if you trade for it locally. Online missions and medals can't longer be done. If you liked BW1, this is more of the same, with some different characters and not much other things change.
Changes introduced in both BW1 and 2 are infinite TM's, lack of soil to farm berries (you were supposed to farm them in the dream world, which is gone), some evolved pokemon that require stones are found in the wild, but rarely and the giant chasm is lowered in level in BW1 as well.
BW2 introduces the memory link so some stuff from your bw1 run affects your bw2 run, and some other minor changes are there, like everstone making breeding natures always pass down. And finally all pokemon sprites are animated.
