A Pokemon game trying way too hard to be taken seriously.
The story is quite honestly trying way too hard to be serious. This could be a response to most of the internet collectively realizing how ridiculous the whole premise actually is, but that doesn't mean the game actually needed to address these points. However, since Nintendo did decide to counter the arguments that the Pokemon universe revolves around legalized dog fights, I can bring up those observations and how Black and White 2 failed to debunk them in any meaningful way. Examine the plot of any Pokemon game carefully and it suddenly takes on a much darker tone; mothers kick their kids out of the house at the ripe old age of ten to go out and collect a bunch of wild animals that have enough power to rival an atomic bomb to prove that they are the best at forcing these living weapons to kill each other. The best possible reason I can think of for such behaviors is that the Pokemon world is in a constant state of warfare, with each region requiring it's inhabitants to learn how to defend themselves in the event of an invasion, which, as I have been informed, isn't a unique interpretation of these games since that idea is swimming around somewhere on the internet. And don't even get me started on the other aspects of their society, such as what they eat.
So, how does Black and White 2 prove all this wrong? Simple; everyone, everywhere, at every given opportunity, spouts off the whole "Pokemon are friends" message. Naturally, this message is present in every single game, but never before has it been so forcefully and prominently shoved down our throats. Your rival character, who shows up far more often than any other rival from any other game, always goes on about how Pokemon are invaluable friends, every Gym Leader says the same thing, more or less, the Professors you're gathering data for go on and on about this topic as well, as does one of the main villains who is, naturally, searching for power at any cost. Look, having the "Pokemon are friends" message pop up occasionally worked fine; by bringing up it this often, it just comes across as ridiculous and, quite honestly, forced. Not to mention hypocritical, since you still haven't provided us with a good explanation for why people should become strong trainers. If you want one that badly, then here's one, free of charge; simply go with a set up similar to The Hunger Games. Each region puts all of it's trainers through a trial of sorts to find the strongest trainer in the region, collecting all of the gym badges and defeating the Elite Four, then sends that trainer to some sort of global competition where the strongest trainers from each region compete to see which one gets bragging rights. You can even keep the tone more lighthearted by making this competition more similar to the Olympics than The Hunger Games. Oh, and before you start pointing out all of the mistakes I might have possibly made in that description, keep in mind that I haven't actually seen or read The Hunger Games. A friend described them to me, so that's basically all I had to work with. It's not perfect, but I haven't seen you come up with anything better Mr. Pokemon developer who probably isn't reading this and probably never will.
I really don't see much point in talking about the gameplay since it hasn't changed in the slightest. In fact, Black and White 2 are about as standard as upgraded Pokemon games get; some of the monsters that weren't readily available before are now readily available, an expanded competitive battling like place was added, rather than replacing the old one, some of the gym leaders have new teams, there are a few new places to explore, and the featured Pokemon is the third part of a trio that the other two games introduced. The Pokedex has been upgraded slightly to show you which Pokemon live in which area, but since it only shows you the Pokemon that you've actually seen, the feature is completely redundant. The only completely new aspect is the ability to change the difficulty after beating the game, a feature that would have been so much better if it had been unlocked from the start. That, and if the difficulties weren't tied to the separate editions of the exact same game, but whatever, you've got to get as much money from us as possible, right. Well, a better way to do so would be to turn the entire series into an MMO, which would have monthly paid subscriptions and would probably be much easier to update every time you realize you forgot to make a Pokemon version of some sort of animal, such as the platypus. Not only that, but doing so would make it a whole lot easier to interact with other people through the game, which is honestly where the series shines brightest.
So, in the end, I suppose the appeal of the Pokemon games has dwindled for both of the reasons I stated earlier; the gameplay hasn't evolved enough to keep me thoroughly engaged and the increased focus on the plot has only caused the series to stagnate. Which basically means this is just an average Pokemon game, with the new faults being balanced out by the new upgrades. Enjoy.