>>17636059BW was like a hilarious attempt at being serious. Prior games had so little storyline that I don't think it'd be fair to take the first one that uses an infinitesimal of brain power and automatically rate it "the best."
I think BW had the best -idea- for a storyline; it unfortunately had awful execution. N came off to me as more of a creep than the intended puppet driven down the wrong road. And of course whenever Plasma was confronted about their blatant hypocrisy, the usual response was "uhh... shut up!" Both of these probably stem directly from the fact that the game's still marketed to kids, and the script has to be dumb enough to cater to short attention spans.
B2W2 remedied this a bit and made N believable, having had two years to think about what Player 1 taught him. Unfortunately Plasma was still over the top, and that made for an awkward mix.
It's painful to read through BW's script. If you jump into B2W2 without having played the first one, just read a quick tl;dr about N and it'll be a much more enjoyable experience.