Well...
Battle-wise? It hasn't changed at all. Rotation battles were gimmicky and didn't get anywhere near enough exposure - I actually forgot they were there - and battle animation is hardly something new...we've had it since Crystal. Constant repetetive motion isn't exactly breaking boundaries here. It was nice to see projectile attacks actually connect with an enemy instead of striking the space above them for a change, but the games have been getting better at conveying a sense of motion over the years anyway, this was something I was expecting.
Gameplay wise, this took several steps backwards, right back to Diamond and Pearl. What happened to all the extra features that were present in HG/SS that added life to the game? Why can't I re-battle Gym Leaders? The little things like that that brought me back to the game, where have they all gone? Once you finished the main story, there really wasn't that much to do, and that in order to get the most out of Black City/White Forest you needed to link with someone else nearby was a huge flaw. We've been online for a few years now - why not online linking? For solitary gamers like myself, it was extremely hard to get the most out of it and, even getting the most from it, it paled in comparison to HG/SS.
This was such a hard game to get into, as well...mostly because you only had access to a couple of Pokemon along the first few routes, and these were not Pokemon I wanted to use. My starter was approaching level 20 by the time I'd beaten the first Gym Leader, and was my only Pokmeon. I was not a happy Buneary. It took a long time before the game finally gave me some Pokemon I wanted to use, and not being able to trade until you beat the first gym was a nuisance as well, because I couldn't even ask someone to give me something decent. It was like the game was doing its utmost to get me to stop playing it, and it almost worked...
I don't see why people are so taken with the story...it's barely there. In a series where the story is exactly the same in each instalment, just with a different team and taking place in a different location, this very slight, predictable twist in motive is a logical step to take (much like the 3DS was the next logical step for the DS) and, like every other Pokemon game, it was lacklustre and uninspiring. This isn't a bad thing - I mean, I know by now that if I want a story in a game, Pokemon is not the place to look - but I feel its been blown massively out of proportion by fans. No twists, no real involvement, no innovation. It needed more to it - MUCH more.
Graphics...well, I preferred HeartGold and SoulSilver, because they were infinitely prettier, but the 2.5D backgrounds (the bridges in particular) were fairly impressive. Some good anime-style cutscenes would have been nice, rather than what they just threw in.
The fifth generation itself...I was expecting them to render the fourth generation obsolete, so I'm not too bothered by that - I'm not much of a competetive player anyway, I haven't the patience for EV/IV training. Some of the designs are extremely lazy, but some of them aren't too bad. As usual, it ranges from the absolutely awful to the reasonably good. I wasn't overly keen on the fourth generation either, but that didn't stop me from enjoying D/P/Pt, and the designs here didn't detract too much (once I got started) from the experience I had playing B/W.
Mostly criticisms here, but don't misunderstand me: it wasn't a below-average game, not for Pokemon. It just wasn't the groundbreaking revolution that people and magazines made it out to be, especially not next to HG/SS which, even without the nostalgia value, were a dream come true, and had so much more content to them. I played B/W much the same way I played D/P when they first came out - with a minimum set of expectations. It fulfilled each one of them, but unlike HG/SS, it didn't go above and beyond them. It was just another instalment in a series that hasn't changed since it was first released. It wasn't bad, but it wasn't exceptional. I could praise the battle system, exploration mechanics and everything else, but...well, those were present in every other game. You expect those to be in a Pokemon game, right? Beyond those standard things, there really isn't anything to praise, because it doesn't do anything new. At least, that is how I feel about it.
