I've been seeing lots of Top Ten Lists online of late, so here's my addition:
Geoff's Top Ten French Churches
Beauvais--Prof. Le Cool and I visited on a weekend excursion from Rouen. Crazy church with a fantastic horloge, some good vitraux, and a propensity to collapse from time to time. Tallest cathedral I've seen. The Gothic taken to ridiculous heights.
Mont St. Michel: More than a church--actually an entire Medieval city and monastary on an island surrounded by mud when the tide is out and water when the tide is in. A great example of ancient Romanesque, and interesting because the nave collapsed and was rebuilt in Gothique style--no easier side-by-side comparison exists.
Vezelay: I love it primarily for that great tympanum, but the crypt with the remains of Mary Magdaleine is pretty damn cool too. You must be prepared to drive for hours through sunflower and lavender fields to get there--how dreadful!
Poitiers: An amazing church, with exquisite grotesque carvings and 12th century glass. Also the interior is actually painted as these churches were intended to be. Most are down to bare stone now. (Also worth seeing is Poitiers Cathedral, with its windows paid for by Eleanor of Aquitaine still extant--also in Poitiers is the awesome 4th century Baptisere St. Jean).
Reims: Oh, yeah, baby. We're getting to the real deal now. Excellent vitraux, but it's extrememly frustrating to note that most of the windows had survived until the Germans shelled the church during WWI.
Amiens: Very similar stylistically to Reims, but with the added bonus of an amazing labyrinth. Love the pale lavender in those 13th century windows!
Bourges: Around the nave are some really outstanding windows, and the surrounding gardens and town are simply wonderful for strolling. Added bonus--Bourges cathedral still lets you climb to the top, and not the view is completely unobstructed for miles.
Notre Dame de Paris: She's got the gargoyles, she's got those fantastic roses, she's got an exquisite situation in the heart of Paris--I've visited five or six times and I'll be back!
St. Chappelle: Visiters to Notre Dame can walk a quarter mile to St. Chappelle and yet they rarely bother--but the second story of this small church takes my breath away each time I visit. All that intact 13th century glass, nearly from floor to ceiling, in such a small space. Ethereal. You must see it before you die.
Chartres: She looms above the horizon from miles away, and I like nothing better than that eager drive from Paris, watching my favorite place on Earth approach slowly. There is no place more lovely, no place so spiritual (and I'm not Christian). The statuary, the crypt with the old Druid well and its altar to Isis and Horus (I mean The Black Madonna and Jesus, of course), and the unbelievably beautiful blue and red glass--this is the pre-eminent sacred space in Europe, and I'm including fantastic places like the Skellig Islands, Stonehenge, Westminster Abbey, and Newgrange. I could visit every day for the rest of my life and be content to do naught else.