First of all, you have to look at it from perspective of phones that cost $500+. Apple never plays in the low end of the market with razor thin margins much like Ferrari doesn't either.
Second, I plan to purchase BOTH phones as I usually have at least 3 phones I switch between depending on my mood. If the Galaxy S could have an IPS display with such a high resolution density, I wish it could get it over SuperAmoled. The only thing great aout super amo is the black levels and the power consumption. IPS displays win on outdoor visibility. Viewing angles and contrast ratios will be nearly the same[. AMOLED loses on color cast and color accuracy. Sure the saturated look some people like but it's not always desirable.
If Samsung could make a Super AMOLED at the capacity that Apple needs and at the resolution Apple needs, I'm sure they would have used it. Simple fact is, its hard to scale up Super AMOLED production at the resolution density that Apple wants.