Some of the posts here cover both of my reasons: longing to see some of the older characters make cameos, wanting to see how Ash's journey ends.
Actually, that's somewhat misleading, as I haven't watched a full episode since AG ended (aside from the contest arc that May appeared in during DP). My zeal for the show, and perhaps the franchise entirely, seemed to dissipate after that. I played through Diamond when it released stateside, but felt it to be more of a chore and something I HAD to do as opposed to wanting to finish it. I caught clips of the first few episodes of the new corresponding series, and thought then that it was simply a repeat of what I had already spent the last few years of my life watching. After realizing that my heart simply wasn't there anymore, I sold most of my Pokemon-related possessions and forced myself to "grow up", as painfully annoying and overused as that phrase might be.
Why am I back? After ending my previous relationship of nearly two years, my mind strangely brought itself back to the show, naming the shipping aspect of it. Back during my early teens, I used shipping as a conduit to express my creativity and feelings, particularly the latter (as I wasn't quite as much of a lady killer back then as I am now lol). After mulling around an idea for a fanfiction for the last several years (never thinking enough to actually start it, mind you), I figure that I should go ahead and attempt to write it, if only so I can stop thinking about it and put the premise to rest. As well, I have actually enjoy what I've played of the new generation of games, and the animated trailer for BW2 is enough to keep me interested until it's released here.
... Oh, and for the women. Why else would I wear my pokewalker to parties?