I'm not too sure i beleive in that story anymore, because i've always wondered the same thing. I'm pretty sure GOD could've known the outcome of the whole situation before he even created ADAM/EVE. HE'S GOD for pete sakes! It seems a little selfish to let all of humanity suffer for 2 people not even knowing what 'bad' was.
The way i see it is if ADAM hadnt sinned than i may have never been born and got to experience life. SO to every downside of life, theres an upside, i guess. :)