*Completed the Vice Kings missions, haven't finished.
Let it be noted that Saints Row is innovative in that the first two Saints Row games effectively have 3 play-at-your-pace linear story arcs, the anthology of missions for each gang feels like 3 games of their own. In addition to allowing the player to choose which to start, it is non-linear in allowing you to play between arcs, so you can finish a mission of one gang's mission arc, and start a mission for another gang.
Another series (Grand Theft Auto) has done this, but not quite in the way where there is always a different mission for a different story arc available to the player for most of the playthrough.
Let it be noted that Saints Row is innovative in that the first two Saints Row games effectively have 3 play-at-your-pace linear story arcs, the anthology of missions for each gang feels like 3 games of their own. In addition to allowing the player to choose which to start, it is non-linear in allowing you to play between arcs, so you can finish a mission of one gang's mission arc, and start a mission for another gang.
Another series (Grand Theft Auto) has done this, but not quite in the way where there is always a different mission for a different story arc available to the player for most of the playthrough.