The Nazi salute is instantly recognisable, burned into the collective consciousness of pretty much everyone from pretty much every generation. It is a symbolic shorthand for what the Nazi regime stands for.
This "Quenelle" on the other hand? First I have heard of it. The only ones claiming it is "sweeping europe" are those anxious to discredit the comedian as an anti-semite. The inventor of the gesture, the comedian himself, terms it an anti-establishment gesture, so who are we to argue?
As to whether he is anti-semitic or just anti-israel, it is difficult to say, although he has come out with some pretty inflammatory and also fairly repugnant comments about things like the holocaust etc. Not someone I would want to socialise with, I don't think. But none of us right now have any clue as to Anelkas motivation in using the gesture beyond what he says - that is was a gesture of solidarity to a friend. That does not automatically mean that he supports all the views of said friend, in my opinion.
If he had performed a nazi salute - ban him for a long time, with a big fine, no question - but this? Far too speculative at the moment...