I would say ISIS is viewed as extreme by a majority of Muslims. When Al Qaeda doesn’t want anything to do with them they are definitely more fringe. But then again I would say Al Qaeda is also extreme, just not as much when compared to ISIS. You might have some extremist Christians but it’s much more tempered.
I do take time for introspective thoughts on this subject and I came to the conclusion that it’s considered taboo to say anything negative on Muslims when talking on the subject of religion. I have plenty of criticism on Christianity as a whole but that path doesn’t interest me due to how common it is to find agreement on the subject.
My opinion/thoughts. When comparing only Christian and Muslim religion, Muslim is more extreme and less criticized