My husband and I spent about a day in the Marais on our trip last month - and it is more of a gay community than a Jewish one IMO (I'd say about 70/30 - maybe 60/40).

The Jewish museum - http://www.mahj.org/en/index.php - was surprisingly good - although certainly not anywhere near like the one in Berlin. The Pompidou is there - but I found the exhibits kind of disappointing.

Lots of singles/pairs/small groups at the cafes/bars - and it is a very active scene in that regard. Just need to make sure you send out the right sexual orientation signals. No problem on our part. We had drinks at a cafe. A male homosexual couple on our left - a female couple on our right. Great talk and no negative vibes - because absolutely no one was interested in anyone else's companion . Robyn