[mousquet]

It's pretty simple. Without its suburbs, Central Paris would only be a sorry provincial town that would be crumbling on the global stage.
There's some kind of saying here: Paris est sa banlieue (Paris is [actually] its suburbs).
That's right. The Hauts-de-Seine and Yvelines départements (read counties in English) have been major economic engines to feed the metro area for long.
Other départements of the metro area like mine (Val-de-Marne) are a bit left behind on the business stage, but we've got a lot of youth and energy. Seine-Saint-Denis is both the poorest and youngest département of our region, and I think it would punch the world with some more business-friendly policy, because the youth can be badly aggressive out here.
By aggressive, I mean business-wise. They are hungry, starving for success.

We all like our central town, though, because it is an outstanding piece of urban consistency and style making the fame of our region. Overall, it is a pretty old town built as some kind of Roman giant, there's no question about that.
The main problem with it has been its ring road built after WWII, when cars were thought to be the major tool of progress.
It actually only turned out a physical barrier, fence or border between Central Paris and its suburbs. While again, the former would be in ruins without the latter.

There are plans to gradually change that ring road into something more urban, like some regular boulevard instead of an ugly expressway, but I suspect it's going to take a couple of decades to implement that kind of plans.
In the meantime, the inner suburbs might turn richer than the central city itself, cause it's also been a laughable NIMBY stronghold.