Yup, I totally agree with you that some of these foods are definitely overrated. To me, Super foods are the ones that have maximum nutrition per calorie. Nutrition is a general term, including vitamins, minerals, protein, fibre, and, yes, antioxidants.
Speaking of antioxidants, while many use this term as a marketing tool, the theory is real and it's proof has been collected in numerous studies, including epidemiological. For example, you could read Dr. Russell Blaylock's website and books. He is a neurosurgeon who spent all his life operating on people brains and collecting medical information that led him to believe in connection between nutrition and health - antioxidant explanation included. He recommends antioxidants to the patients before surgery due to huge release of free radicals during and after it. He has data. And so do many other researchers.
Anyway, whether you believe in it or not, eat your greens for the multitude of health benefits.
Speaking of
Super foods to boost immunity, you want to stick to the whole unprocessed foods; top source of vitamins and minerals would be sprouts and greens, vegetables and grains.