In general I agree with all the answers from the Michigan agents. Our local market has been trying to say the least.
If a project will add value for your family while living in the house and return on the money spent is not an issue, then by all means finish the basement and enjoy it! Most homes with finished basements will show more favorably than homes with unfinished basements.
If the main concern is increasing the sales price of the home, then a little research should be done before undertaking the project. You really need to look at what other homes in your area sold for, what didn't sell for , and what is currently for sale. Go out and look at open houses or active listings to get an idea of what is out there.
One additional thing to consider is how will the project be paid for? If this project plus what you currently owe on the home will put you underwater, that will create additional challenges when you try to sell the home.