Not once in the three decades that have elapsed since my arrival in Paris had I mounted in the Arc de Triomphe. Not a grievous oversight, as I realise now that I have been up there.
However : The view is neat, the queues are a lot less lengthy than at a certain other Parisian vantage point and a recent photo exhibition showcases uniforms of unknown soldiers from various wars.
If you do want to view Parisian rooftops, apart from the Eiffel Tower, there is also the Tour de Montparnasse or Centre Pompidou. Among, certainly, others.