There's a lot in BW that I really like. I can safely say that these are the games that brought me back into Pokémon gaming... something I hadn't really done since Emerald, partially because I didn't have DS. I tried SS and Diamond, but neither managed to fascinate me as much as Black did. Though I'm definitally going to try to finish SS at some point.
Things I liked about Black and White:
-Story. Huge plus! Previous games mostly revolved around you getting badges, meeting an evil team, fighting them,winning, and beating the E4. BW, had a story that went further, and even gave the game a wonderful climax and ending.
-Characters. N's not the only one who's highly ranking in my favourite character's list (not Pokémon-exclusive), White/Touko is another one. I shouldn't forget Cheren, Bianca, Juniper... and others. I didn't have that many favourite Pokémon characters in the past, but now there are quite some.
-Music: Ending theme, Route 10, Relic Castle, Team Plasma Battle, Emotional Piece, N's Farewell... Previous generations had remember-worthy songs (think of Route 1 (Kanto), Goldenrod City...), but Black/White's music is something else. Specially the "Final Pokémon in Gymbattle" song was a very nice flashback to the first generation.
-Graphics/Unova: Lovely region, though I don't like Chargestone Cave, Twist Mountain and Route 4. |D (I do like Chargestone Cave's idea, just don't like traversing it.)
-Pokémon: I'm someone who adores the 5th generation, it definitally has some of my favourites.
-Other: The pose when the MC finds an item (felt very Zelda-ish), Seasons and seasonal changes, evening and morning, being able to add to the music by talking to some NPC, perpetual TMs, shaking grass, etc
The whole animated sprites thing didn't feel that unique to me, seeing how they moved before in Crystal and Emerald. Having them animated throughout the entire battle was rather fun, though. :'D