You are correct in many parts of this big city, Marseille, which is the second largest city in France, you will find more similarities with Rabat (Morocco), Algiers (Algeria), or Tunis (Tunisia). This situation will continue to evolve in the future to become even more emphasized because traditionally Muslims have a much higher birth rate compared with Christians.
As result of the situation of a large Maghreb population, Marseille has the most fanatical soccer aficionados in the French League 1. Other French league teams with fanatical support include Lens in the north, and St Étienne - although this last team is going through hard times now.