Comics creators are, without notable exception, compulsive thieves. There's no shame in it. It's part of the charm of the medium.
Stan Lee started his career as a magpie among magpies, producing almost two decades of incredibly derivative comics before hitting that amazing stretch in the early Sixties and even then continuing to borrow whatever DC's lawyers hadn't nailed down. None of that diminishes his legacy. However, his tendency to dismiss the work of other creators does.
Over at Stanley Stories, Frank M. Young has an example of Lee ripping off one of the giants, John Stanley, perhaps the best writer of comic dialogue to ever work in the field.