I think that the simplicity you were going for worked, although i can't help but feel it's a little...too simple. I couldn't help but feel that the rhyme scheme AABB- that's great, but i think your lines were TOO short to carry off this rhyme scheme.
Even if you editted it slightly to make it just that bit longer for example;
What if the stars fell from the sky?
Would people wish to never die?
==>
What if those glistening stars fell from the sky?
Would people, here on earth, wish to never die? .
You see my point? you only have to add a few words and it makes a big difference.
Anyway, on to the positives;
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I love the repitition of "what if" at the beginning and end of the poem, I think it has a really good effect on the poem, and breaks up the simpleness of it slightly.
I like that this poem probably represents what the average person actually thinks. Everyone sits and comtemplates these things, everyone sits and thinks those "what ifs". And i think you really reflected the questions that everyone ponders at some point.
I love the end stanza; and the end line
"what would that mean for me and you".
Everyone has someone that you think that about.
5/5 still, as the negatives didn't over-weigh the positives =)