Why haven 't terrorist attacks happened in Germany, Italy, Spain, England or Northern European countries but keep happening in France?
One of the main reason is that when you hit France, you got free world-class media coverage for weeks which helps a lot to 1) spread terror (your goal as a terrorist) , 2) demonstrate your strength globally and 3) raise interest and ideas in the mind of new recruits or other potential attackers. So far this media strategy is 100% efficient with every attack in France being subject to an incredible amount of media attention.
It is true that there is a bigger Muslim community in France but really, most are peaceful, and the radical ones belonging to terrorist groups could aim at anywhere else on the planet. As Raul Castro showed in his answer, there have been attacks in many of the countries you named, not even mentioning Iraq, Syria, Pakistan, etc.
France is a big symbol with an enormous media echo chamber, so attacking France is super efficient in bringing terror and destabilizing the relative peace state in the West.
This text was originally published in quora.