It's not the same in France definitely :
From an architectural point, it would be quasi impossible to destroy and rebuild the Parc des Princes. The urban/architectural laws France have are extremely restrictive, above all in areas like Paris where historical buildings are highly protected. The urban tissue is quite dense and the inhabitants hate change with a passion (look how Roland Garros stadium have difficulties to increase its size). It's a fact, the french (well I could say the parisian but it's a shared trait in the whole country IMO) love their city and don't want drastic changes.
But even with 50,000, the Parc was always known as a great crowd. For the '16 Eurocup, I think there will be some building works (?) to increase the size but this is just make-up.
Finances in Spain are worse than ours but they have 2 huge clubs that have a worldwide shine and football legitimacy. Monaco and PSG could be France's Real and Barça (Lyon should have been but there but they never passed that glass ceiling). They have legitimacy (it's little but still) and they now have money. Let's see if these two could increase L1 popularity and gain trophies in the next few years to really be a Top 5 league (among Spain, England, Germany and Italy) because honestly, these days, we are the 6th nation behind Portugal.
About Paris and the number of clubs, you should read this :
Un "second club" à Paris est-il possible? - Les Cahiers du football (in french unfortunately, but maybe Google Translate can help.
Anyway, look at the images to understand :
There are 7 "parisian" (it includes Ile-de-France clubs, which is the parisian region, from a strictly parisian point, there only is 3 : PSG, Paris-FC and Red Star) football clubs : 1 in L1, 3 in 3rd division, 1 in 4th and the 2 last in 5th.
Paris compared to London, Moscow and Berlin...