The game of cat and mouse between Light and L is quite compelling. I know that goes away, and I just can't see how the show could possibly maintain its appeal without both of those characters. I also know that there are at least two other Kiras (I've met Misa, who is one hell of a crazy bitch1), but I just cannot see how they can be so interesting. After all, Light knows what he's doing because he's a freaking genius that has studied the arts of law enforcement. Sure, he gets sloppy from time to time, but for some reason, he always seems to win at Xanatos Roulette.
That said, I'm not quite feeling the slashy goodness that others seem to get from this series. I mean, sure, I can see what the fangirls are on about, but frankly, I see Light as perceiving himself as so superior to the rest of humanity, L included, that he couldn't possibly bring himself to love as mere mortals do.
Holy crap, I'm slowly turning into an otaku. I mean, what other kind of person would have a Yui Hirasawa plushie on his bag (don't judge me!)? Save me, Internets. You're...not much of a hope, are you?
1. Oddly, I felt a chill run down my spine when I first heard her voice. I looked her up on the character sheet at TV Tropes and found out why: that's the same person that did Haruhi and Konata, both characters that have terrified me for totally different reasons.