You missed out the huge number of purely European terrorist organisations that have been around in the last few decades.
You know the lesser known groups such as the IRA, the PIRA, the real IRA, the loyalists (and that's just some of the UK/NI ones), basque seperatists such as eta etc. The vast bulk of terrorist attacks in Europe over the last 20 years have been by the likes of eta.
Isis have "just" had a few high death count attacks, but even then Brevik killed a huge number of people as a lone nut.
It's relatively recently with the rise of Isis and Al'quada that we've had any real problem with Islamic terrorists.
There is a problem, but in terms of attacks the ones by the likes of ISIS in the west are far rarer than the ones by the various "Christian" (if you're just going by the religion they claim to follow and ignoring the political aspect) terrorist groups, however they get a higher death toll because they're well financed, well trained and the people doing them are willing/expecting to die in the attacks so don't even try to get away.