I'm not sure yet but maybe the solution for having more competitions in the French League is to have a more rich owner for the other teams as they have than in PSG. Since they have good a rich team in PSG they can have much better and more expensive players and coaches which makes PSG a much better team than other teams.
That's why even if PSG is not in the good for many other teams like Marseille and Monaco try hard they still can't have a fair competition with PSG.
Recently we saw rumors about Marseille and maybe the Arabs are interested in buying this team and hiring some superstar players for them but this team but until that time I don't think if we can see any competitions in the French League.
The competition the French league is one which i don't see centering around the wealth of the owners of the teams, PSG does have a really wealthy owner but i at same time do not see that as the only reason they are at the leading point of the French league but their depth and their squad strength which is something others can actually build without having to really having to buy big star players but with building the team to that point where they will be able to get them the level of stability that PSG has gotten enough to compete with them.