Nuts would have been one of the richest sources of macronutrients by density in our ancestral environment, and they wouldn't have been available in great quantity, which is probably in large part why they're such an addictive food.

(My girlfriend has a nut allergy, and since I've started having to keep track of nut content in foods, I've noticed that the "snack" aisles in grocery stores can be divided, with fairly little remainder, into chips, pretzels, and nut-based foods.)

Liver is higher in micronutrients than nuts, or just about anything else for that matter, and I suspect that it avoids being a superstimulus to our senses because it would be one of the few food sources in our ancestral environment that it's actually possible to get a nutrient overdose on (many species' livers contain toxic concentrations of vitamins, not to mention the various toxins it's filtered out of its host's blood.) In terms of macronutrients, nuts have a higher calorie concentration than any animal tissue other than lard (a cut of flesh which is as calorie dense as nuts would have to be about two thirds fat by weight.)

Lard of course is not known for being a very tasty food on its own (it's also very incomplete nutrition,) but is used extensively in cooking foods which people have a pronounced tendency to overeat.