If an urban mall, definitely Campus Martius. A mall has been under consideration for this site since the 70's. In fact, when Hudson's closed, they indicated they would return in a mall format if another department store anchor could be found.

Do I think such a mall would work? Probably not, given the generally dismal performance of urban malls in the U.S., and the extreme challenges present in Detroit. But, if such a mall could succeed, then Campus Martius would be the most likely spot for success.

If a more conventional suburban mall, I would go with East Jefferson [[say the Uniroyal site, or the wastelands close to GP Park), which have lots of space, plenty of strip malls already, and decent traffic and disposible income.

Keep in mind that malls aren't being built very often these days. The few that get built are generally middling-to unsuccessful, and are often in the smaller "lifestyle center" format [[see Partridge Creek or Village at Rochester Hills).