Six Mile Road and Seven Mile Road (6 and 7 miles from Downtown Detroit, respectively) are far worse for crime than Eight Mile Road is.
Eight Mile Road is the true divider in Detroit - anything inside Eight Mile Road is sketchy. Outside Eight Mile Road is white and suburban.
The rapper Eminem now lives near a golf course and country club near 28 Mile Road these days. Before that, he grew up at 19946 Dresden Street, between Seven Mile Road and Eight Mile Road - a blighted area. I walked past his old place all the time, although I watched my back.
I have spent a lot of time in the rougher parts of Detroit. Generally the gang activity is small neighborhood gangs, not the big national franchises like the Bloods and Crips, although there's a few exceptions. The Mexican/Hispanic gangs would be over towards Southwest Detroit, but I know nothing about them.
One gang who used to get a bit of attention was YBN/PBS, who were also a semi-successful rap group in Detroit. Truthfully, most of these guys are brainless and have to resort to crime and muggings just to make a few bucks. Others are immature suckers lured into the supposed 'glamor' of the rap-gangster lifestyle.
The Italian mafia, or what's left of them, would likely be in Grosse Point, which is a nice area miles from the rumblings of Downtown. I never went that far out of town.
It's more national gangs in Detroit though alongside Crips, Bloods, GDN, BDN, VLN, LKN, LCN, MLDN there too.