Those streets of Paris are certainly a gamble. Diagon Alley was built up throughout several books and movies as a key location in the lore. It is visited many times and viewed from several perspectives through Harry's eyes: as a place of childhood whimsy of the first visit in Philosopher's Stone, showing the first hint of a darker side to wizarding society in Chamber of Secrets, giving the taste of the wizarding world outside Hogwarts in Prisoner of Azkaban, being mostly inaccessible to Harry as he clashes with the ministry in Order of the Phoenix, being an indication of dark times and depression in Half-blood Prince, and finally the site of the heist in Deathly Hallows. It's an iconic place the reader (and viewer!) is fully immersed in and gives a real sense of recognition between books and movies. It's a location full of iconic sights and shops.
Likewise, Hogsmeade is given somewhat less attention in the books, and certainly in the movies, but it is adjacent to Hogwarts itself, which is *the* iconic location for the entire series.
Meanwhile, 1920's Paris is visited in one scene in what is by far the most disjointed and messy movie in the franchise. There's one passing reference to one French wand shop in Goblet of Fire. That's all the material the series gives to work with. No matter how excellent the execution, the place won't have the same draw and recognition that Diagon Alley has, not to mention Hogsmeade. That's probably why they saw the need to connect it to a more recognizable location (the Ministry of Magic, which only appears in the fifth and seventh books/movies), even though that connection makes no logical sense.
I have faith that Universal will manage to deliver some truly great rides, but in the long run I doubt it will rival the other two Potter locations for popularity.
