For the US, that's likely. For Europe it heavily depends on how you count. Is a far-right loner murdering a politician the same as a group of Islamists murdering 200 people in Madrid? That is, are you counting events or impact? By events, the far right might (which is hard to calculate, because it's fuzzy, e.g. Turkish Grey Wolves are considered to be a far right group, but are Islamists) be more than Islamic terrorism, by impact they certainly are not in the last decades.