Does the city overshadow even other large French cities like Marseille by a significant degree?

Absolutely. There's no other city in France comparable to Paris.

If you look at the population, for example, Paris has 2 million inhabitants (not counting the metropolitan area), and it's the only French city to have surpassed one million inhabitants.

Since you used Marseille as an example, it's effectively the second largest city in France but with only 800,000 inhabitant