By a stroke of uncannily good timing, I've only recently completed
this list of my Top French horror films on Letterboxd.
It's ordered chronologically, but my Top 5 would be:
1. Les Diaboliques (1955)
2. Eyes Without a Face (1960)
3. The Iron Rose (1973)
4. Don't Deliver Us from Evil (1971)
5. The Grapes of Death (1978)