I’m completely with the Prof on this one. Singer may tell a hell of a story. The rest of the movie may be in perfect order (the sets look freakin’ fantastic). Routh worked his ass off to add muscle mass, and apparently they had to refit the suit twice during shooting because he kept gaining.
But they freakin’ designed the suit to make him look smaller and leaner, and that. Just. SUCKS.
Addressing prior points:
- Superman was not meant to look like he was average size or a normal man. Ever. From his inception he was designed to appear as the pinnacle of human development, “super” in appearance, in capacity, and in nobility of spirit. Shuster repeatedly said that he based the athletic stunts of Superman on Douglas Fairbanks Jr., but in terms of physique he found inspiration in the strongmen of the era.
That’s why in the original drawing Superman was often depicted wearing Greco-Roman type sandals/leg wraps. Given the era, photos of John Grimek may well have provided the model for some of the original Superman sketches.
He wouldn’t be able to realistically get big without challenge to his muscles? Okay, we’ll ignore the improbability of a man who can fly and shoot laser beams from his eyes, and focus on his build.
This is a being who comes from an society so scientifically advanced that they make ours look like neanderthals. A society where couples are chosen based on genetic compatibility in creating the most perfect children possible – who are then born not from their mothers, but from artificial birthing chambers.
Chances are, he’s at least partially genetically engineered to maintain peak fitness with minimal effort, given the Kryptonian disdain for ‘earthy’ activities.
He’s then launched across the universe and ends up on a Kansas farm, where his powers are slow to develop. In his formative years he helps with the heavy labour of farm chores, testing his prodigious strength against bigger and bigger tasks. That perfect genetic makeup is stuffed daily with wholesome, home-grown foods that manage to turn lesser men into blocks of muscle.
2)His abilities weren’t conceived of simply as a notion of “maybe the girl would like me more if I could…” Nor were they really purposely conceived of based upon psychological theory. 
The original Siegel & Shuster Superman was actually a villain in a pulp-fiction sci-fi world. They abandoned that idea and revisited it again later, depiciting him as heroic the second time around.
Siegel & Shuster were Jewish kids living in a poor area of town. They saw a lot of things, a lot of social injustices, that really pissed them off. Superman isn’t the fantasy of getting the girl – he’s not the adolescent power fantasy that certain pop culture analysts in the press would like to paint him as – the character is meant to be the fantasy of altruism. The power isn’t the fantasy, it’s the vehicle by which the fantasy is achieved.
The first stories of Superman depict him terrorizing corrupt politicians, ending wars, capturing a murderer and saving a man wrongfully convicted of murder, and whuppin’ on a wife-beater.