I'm going to play Devil's Advocate and argue that from a narrative perspective there is some cause for question here as to whether Black 2/White 2 were actually better. I think in terms of gameplay and content, it's fairly easy to argue in favour of the sequels being better than the originals, but in terms of "story" content - and how I loathe to use that word in conjunction with Pokemon - I'd actually argue against it.
Now, I in no way think the narrative of either of the Gen V games is acceptable, or even noteworthy. In any other JRPG it would have been criticised as utter drivel and laughed right out of the market; it owes its success solely to the Pokemon name (and the repetetive nature of the games, so that every minor difference is noted and blown way out of proportion by the fans) and not through any creativity. It's pitiful even by 90s standards, which Nintendo seem to hold to religiously when it comes to trying to give their games an actual plot. That said, sequels usually recycle elements from the originals, and there was very little to differentiate B2/W2's story, really. A lot of key characters were reduced to mere cameos - and they were already NPCs!- and there was generally very little feel that this was actually a sequel in the truest sense, as you were playing with an entirely different character and the major players from the last game had moved on with their lives. THEY certainly didn't need a sequel.
There was no real sense of continuity or purpose, and it was a lot weaker for it. Had we visited some more new areas, or had the NPCs from the previous game returned in some meaningful form more often, then perhaps it might have been able to justify itself. This was very much an unnecessary sequel in that, bad as it was, Black/White had a story with an ending. They didn't NEED a sequel. There were no real loose ends to tie up, or things that needed to be explored, and as a result the entire thing was even more banal and pathetic than usual. It in no way justified its very existence from a purely narrative standpoint, as it had nothing left to narrate.
In terms of content, I would say yes, absolutely. But in terms of narrative? These games weren't needed, and they suffered for it.