This post started out differently but I didn't finish it before I actually played the game so now I'm going to write a review. I've had about five hours play time on Black 2 at this point and managed to get a couple of badges so far and the verdict is that Black 2 feels a lot like Black and that's a good thing.
The battle mechanics are essentially the same as they were except the selection of Pokemon is a lot different. In fact, the selection reminds me a lot of SoulSilver. I started with Oshawott and I have a Pidove but those are the only two Pokemon in my group right now from Generation 5. There are a lot of Generation 1 and 2 Pokemon in the first areas to encounter. Playing the game some more reminds me a lot of SoulSilver.
One thing that is definitely missing is challenge. The first three gyms that I have worked through have been pretty darn easy. Challenging the first gym was the biggest challenge at this point because I did not have a type advantage and there was no really good place to level up at. The other two gym leaders had major type disadvantages. The "Poison" gym leader was a joke and fell to a Magnemite that was 4 levels lower. Sonicboom to death. The "Bug" gym leader had Swadloon and Leavanny which has 4x damage from Fire which made them one shots to my Growlithe. I've also noticed lots of chances to have Pokemon healed in large areas to prevent the need for lots of potions or running back and forth between the Pokemon Center. But these things really aren't new, Pokemon Black was very easy on the player as well, reserving the challenge for the parts of the game after the game. You lost the game. For this reason, I hesitate to say "Pokemon Black 2 is easy" because it very well could be difficult by the end of the game and I could be over grinding and making my Pokemon higher levels than they need to be. I am also blessed to be getting Pokemon that I really like having.
But it is kind of fun experiencing the game again with slightly different characters and areas and the music is fantastic. While that might sound kind of funny since the music is very similar to the previous game, the existing pieces were touched up and the new pieces are great for a portable. Giving every trainer an animated intro was an excellent touch and the game retains the speed of generation 5. Looking closely at some of the Pokemon, their animations are different, at least the starting Pokemon.
Now that I have finished it, I was shocked by how much easier it was. The game seems to force you to have higher level Pokemon by the end so when the Pokemon jump to the 60s in the post-game, your Pokemon are already there. I've started collecting the wide range of legendaries available and have experimented with the Pokemon World Tournament and I've been very challenged. I am enjoying it.
The verdict? The game isn't as good as Pokemon Black because Pokemon Black exists. If this had been the first game in the series, I would have been extremely satisfied with it. Because I've already put so much effort into Black, this one doesn't feel quite as good. And that is sad.