Looking for games similar to Mafia/Mafia 2.

Maybe you'll like LA Noire.

Saints Row series (at least up to the third).

Sleeping Dogs, perhaps.

try sleeping dogs

Sleeping Dogs is probably my favorite "GTA Clone".

For open world games, check out the Godfather games.
https://en.wikipedia.org/wiki/The_Godfather_(2006_video_game)
https://en.wikipedia.org/wiki/The_Godfather_II_(video_game)

Mafia III sorry

The only other game I can think of right now which hasn't been mentioned yet is The Saboteur on Origin.

Maybe The Darkness 2?
More Splatter/Brutality but an interesting Mafia-themed story.

the nutshack the video game

Watch Dogs 1-2, Driver San Francisco (?)
Total Overdose :D
Just Cause 1-3

Predecessor of Sleeping Dogs: True Crime: Streets of L.A. and New York City (not on Steam though).
Kingpin: Life of Crime (on Steam, but not purchasable in my region)

Maybe mafia 3? XD

I heard Mafia III is pretty similar D:

I happened to play LA Noire and Mafia 2 almost at the same time and they are veeeeeery similar.