I also think it depends on who you want to convert*laughs*
I, for example got to him through the infamous vanilla-live, but I'd never show that to someone who isn't into yaoi or at least open-minded enough to not say "OMG, he's so gay!"^^;;
so, PV-wise, I'd choose Returner, perhaps...just because it's very Gackt-ish and at the same time visually very pleasing, even to someone who never heard J-rock before^^