Ian, I think Nintendo went with not letting you trade prior gens in R/S/E was because there was more money in the Gen I remakes.
That poll Mop posted just shows that nostalgia, above all else, reigns supreme. There also could be the added impact of not being a school kid when the new Pokemon game comes out, so you aren't surrounded by people to trade, battle, and share tips with.
If we're ranking the Gens, I'd go with IV, V, II, III, I. I only put the third over the first because of the Gen I remakes.
Also, for the record, HG/SS are the best games; and Crystal version had story elements.