I believe that ghosts exist, yes. But my view is based on the Bible-
(From Luke 11)
23 “Whoever is not with me is against me, and whoever does not gather with me scatters.
24 “When an impure spirit comes out of a person, it goes through arid places seeking rest and does not find it. Then it says, ‘I will return to the house I left.’ 25 When it arrives, it finds the house swept clean and put in order. 26 Then it goes and takes seven other spirits more wicked than itself, and they go in and live there. And the final condition of that person is worse than the first.”
Spirits exists, yes. And that includes our own spirits. And I believe that those who are not saved are left here until the day of judgement.
As for like, the ghosts that interact with us, through mediums and ghost hunters and the like? Absolutely not. We already know that fallen angels interact with us daily to lead us away from God. God tells us not to communicate with the dead, that such things are an abomination. Satan gives us false signs and wonders to lead us away from God, and I believe that "ghost hunting" is no different from anything else he does.