I've always wondered why that is. What's the history behind it? I know it goes back at least as far as the late 19th century.
I think the main reason is the huge popularity of Japanimation in the 70s, 80s and early 90s. Any french person who was a kid in those days would tell you that Japanese shows were all over the place ( actually my avatar and name are a testimony to that period... ). Dragon Ball Z, Saint Seiya, Sailor Moon, Grendizer, Hokotu No Ken, City Hunter, Captain Tsubada and dozens of other shows were so popular than it led to a huge interest in manga. Actually many of those shows were based on manga.
That period imo led to the popularity of Japanese videogames in France. JRPG for example were massive in France during the Super Nintendo and Megadrive era ( SNES / Genesis ). There were the closest thing to a manga you could get on a console. One of the reason Nintendo was more popular in France during the 16bits era were the RPGs. Sega was pretty big in France during the 8 bits era ( I won't be surprised if the Master System did better than the NES ). The RPGs on SNES definitely helped Nintendo turn things around in France.