While it is a copyrighted term that was originally made for marketing purposes, the fans and media have pushed it to become a symbol. That's why it is somewhat relevant today when people argue that Detroit isn't passionate enough to have the Hockeytown moniker.
In any event, Hockeytown as a symbol represents the entire state of Michigan (as well as some nearby parts of Canada), and as such, there shouldn't be any argument against us bearing the title. Michigan claims more youth involvement in hockey organizations than anywhere in the country; there is a strong college history pertaining to hockey, including an annual collegiate tournament based around teams focused primarily around Michigan and the Cold War (which was not only a monumental occasion for college-level hockey, but for the game in general); While times are currently hard, Wings fans still make themselves heard at local bars and opponent venues (general knowlege that the Wings have the best nation-wide support). There is never a quiet night in Hockeytown Cafe, which is appropriate enough; The passion for the Wings regardless of whether corporate executives or blue-collar Andys fill the Joe tops that of the Pistons, Tigers and Lions, which cannot be said for any other state. Oh, and I suppose I should mention something about four Stanley Cups, five finals berths, countless Presidents' Trophies, and Hall of Famers that have passed through the area, but then it wouldn't be fair
So even if you take the "Hockeytown as a symbol" route, I still don't see any problem with it remaining with Detroit.