It’s not so easy to get an overview over Paris, even there are no skyscrapers. But the houses are still high enough, to avoid overlooking the city. There are also not hills around Paris, except the Montmarte Hill. So, when standing in front of Sacre Coeur, you can have a good sight over the city. You can also climb up the Eiffeltower.
But I’d recommend going up the only skyscraper of Paris. With around 200m it’s smaller than the Eiffeltower, but you can also see the Eiffeltower. But from where?