My point, and I suspect Wellington's, was not that Scott over came the Napoleon of the Americas, but that he overcame the natural obstacles an invasion of Mexico throws up. A lot of the problems Wellington faced in the Peninsula were logistical.
A General's achievements should not be measured solely in terms of his opponents, but should also account for what he achieves, where he achieves it and with what material. Scott led a force made of borderline professionals and volunteers deep into the interior of an underdeveloped and in many senses "unknown" nation (to Europeans and a lot of Americans anyway), won battles, occupied its capital and withdrew intact. When you account for the variable quality of his subordinates, I begin to see Wellington's point.