Never really finished B2/W2, so I can't offer much of a detailed opinion on those, aside from the fact that I have literally over four-hundred hours logged on my copy of Black and I put Black 2 down before my party was level thirty and made more of an effort to pick up my other games than that one. Yikes.
I really loved so many things about Black, especially my copy, considering that I squeezed LV. 100s and shinies out with a lot of effort, but that's probably bias, considering that I don't know how many other people have had the same luck. Even in the face of generic or even bad luck, I feel like Black brought a humongous amount of fresh, new content to the table, and raised the bar perhaps a little too high. Perhaps that's why I didn't think too highly of the Gen 6 games, though the race customization was really incredible and I loved that element of diversity.
Either way, continuing on that train of thought, a large part of my reasoning for really loving Black was the fact that it was my first later generation game; I'd always played Pokémon XD, Pokémon Yellow, Pokémon Blue, etc., and I never got around to playing DPPt because we never wound up buying it (we bought a cat that year instead and just never made up for it). The only newer games I had played were HG/SS, both of which I received for Christmas sometime after that.