Yeah, Detroit's got some terrible urban decay. I volunteered downtown (right by the Ambassador bridge and Mexican town) for half of last year and frankly, half the houses are completely terrible, but the other half are nicely renovated homes and look great. It's like, one block shitty, one block nice.
It doesn't help that all the white people moved to Livonia (one of the now-whitest cities in America) just down I-96. I think the population of Detroit's now down to levels not seen since the 20's.