Michiko to Hatchin, Gangsta. Recommendations
Both shows are centered around the underground, crime filled lifestyle. Both of the shows are influenced by drugs, gangs, sex, and violence which add together into the overall gritty, slummy, and bleak atmosphere. Michiko to Hatchin differs however by having a quite different approach to it's story by presenting a more linear plot while Gangsta' story line appears to be driven more through character development.
Same studio and similar premise/world.
This isn't a very conventional recommendation but I still think they're comparable. They're Manglobe titles, both of which have a rugged, urban setting and explore the underbelly of whatever society they're a part of.
While Michiko is a lot more light-hearted in presentation and formatted in a "road" journey depiction, as oppose Gangsta's city-trekking and often dower aesthetic; their similar setting and character designs make them feel like they share the same universe. A "two sides of the same coin" situation, if you will.
If you are into the crime setting of Gangsta, Michiko to Hatchin may be an anime you'll really like. Not only does it have a similar feel as Gangsta, but it has a heartwarming story to it. Both animes are made by Manglobe studios, so I can see why their so similar.
Both deal with Gangster-like type of life
They have the same character characteristics
They both have serious and fun moments well balanced