Depending on your point of view, Apple's products are either A) Clearly superior or B) Not obviously inferior. For a not insignificant number of people, their choice of smartphone is a personal statement. Attacking products that people love is not a good way to create converts.
Attacking products that clearly suck works until a point. Then it starts to feel like a bully beating a defenseless kid. Microsoft's advertising feels more like a nerdy kid who spent all night thinking up clever and witty retorts, only to fail miserably in delivering them when face to face with the bully. The crowd of cool kids don't laugh with the nerdy kid, they laugh at them.