It seems that items which provide benefit to AD champs provide more benefit across the board to champs who have a high attack speed. What do champs with slow attacks (like say, Alistar) do to keep up?
An attack speed item benefits a faster attack speed more, because 25% of a big number is better than 25% of a small number.
An attack damage item applies its bonus damage more often on a high attack speed champ.
Crit is the only stat that seems fairly equitable... at least, in isolation. Slow attackers typically have higher base damage, therefore they crit harder than a fast attacking champ. Once you start putting +damage items on a fast attacking champ, however, he starts hitting hard too - but more often.