Towered
Superstar
I can't give a precise answer but I'd argue probably not. Internationally I imagine some of the bombed out cities in Europe and Asia, as well as heavily redeveloped ones (especially in East Asia) have lost virtually all their pre-WWII buildings in some areas. In North America I'd say Toronto is still pretty average (though I'm also gauging from my own perception, so take this with a grain of salt). Detroit has been massacred, large parts of Manhattan have been redeveloped (even if a good deal of the original stock does remain, look at the Lower East Side or the other housing projects that clear cut whole swathes of the city) and I've even seen the Montreal forumers (on SSP and Mtlurb) bemoan how much Montreal lost. Halifax is another Canadian city that has seen a lot of it's pre-WWII buildings destroyed too, as has Hamilton. And finally, from my own perspective, I'd argue Guelph is a pretty sad example of old buildings being destroyed to "modernize" the downtown (or from fires). The loss of the Carnegie Library, the YMCA building and the Post Office (as well as Quebec Street and St. George's Square) did a lot to destroy downtown Guelph and have left it a hulk of its former self. The fact it's as vibrant as it is is actually really impressive considering how much of it was destroyed over the years.
Most of those destroyed European cities actually rebuilt their old heritage buildings from scratch though, unlike here where our collective ambivalence seems to just give up and say "oh well".