Emma is the only one who could break the curse. Henry is Emma's child. That's like, 1 1/2 Emma's. Even if you don't agree with that train of thought, which I'm not sure I agree with myself, it's logic. Emma has to break the curse, so no other "twoo wuv's kiss" will work b/c it doesn't involve her. Factoring out the huntsman, because come on, he saved Snow White and Emma is Snow White's kid so that's just icky.
Don't you just hate it when the Dark One turns you into a rose and his house-maid cuts off your legs?