I just finished black 1 and let me tell you that Pokemon games can keep you interested and you might get caught investing a sh*t load of time into it. Get black 2
Both are a great game so you should buy both.but if you want to buy only one first,you should probably buy Kingdom Hearts 358/2 first because you can finish it faster than Pokemon Black 2.
well.. which series do you like better? KH is more mature (even if the stereotype is it's kiddy, since it is disney), and it's more action oriented. actually has a real story unlike pokemon.
personally, while pokemon is fun at times, if you're just going for solo play then I'd go with KH.
the better game is subjective.. really depends on you. black 2 isn't even all that different. it's the same old pokemon, which a bunch of new little features and online stuff. there's dreamworld, which is an actual online site you have to go to, you can play these mini games and get pokemon there..
it's awesome, but it's still just pokemon. if you are in the mood for it, then get it. otherwise KH would be a better choice. really depends on your mood, and your own opinions.. not random people's opinion on which is better.