As far as I understood, "high fructose" in HFCS is only high relative to the corn syrup that was hydrolyzed, but not processed with isomerase, i.e. essentially compared to corn syrup with no fructose at all.
Most commonly used HFCS varieties contains 42% or 55% fructose [1], which compares well with 50% in sucrose.
[1] https://en.wikipedia.org/wiki/High_fructose_corn_syrup#Compo...