Ah, the wishful thinking argument. Fair enough. Thank you for the opportunity. Of course you are talking about religious faith, not other kinds of faith… like faith in science or faith in your best friend, right?
Faith in general is something everyone has. We would not take a step unless we had the faith that we would not step into a deep hole or off a cliff. We would not turn the key in our car but for the faith that it would start. This general faith is not wishful thinking but based on experience. After many decades of life (experience) of interacting with God and daily seeing answered prayer, my present religious faith is very much like this everyday faith.
However, when I first came to Christian faith, it was a risky step into the unknown. “When we come to the end of all the light that we know and we are about to step off into the darkness, ‘faith” is knowing one of two things will happen: there will be something solid in the darkness for you to stand on or you will be taught how to fly.” (Edward Teller) This step of faith was much closer to wishful thinking, true, but it was also an issue of personal trust--- more like when my mother told me as a child to not run out into the street and to wash my hands before eating. After being exposed to the New Testament scriptures, I had come to trust their Author. As Jesus (the Good Shepherd) said, "My sheep hear my voice and follow..."
Faith in something that is not real is indeed wishful thinking. In this I agree with you. And like the placebo effect, such faith can have a short term positive outcome (like sugar pills). But faith in something that is real will be proven out over time. I cannot speak for every person of faith, but I can certainly speak as an old Vietnam Vet and scientist … that I get constant evidences of God’s love and leading … and have for most of my longish life. It is not wishful thinking when it works over many decades. The ground has been quite solid.