This is a rant, so be warned.
If I hear anyone else (be it in person, in the media, or on a message board) compare radical Islam to radical Christianity, I may have an annurism. Why is this such a popular comparison? Personally, I can't remember the last time a Christian group blew something up, beheaded a helpless kidnap victim (or kidnapped anyone, for that matter), shot men, women or children, crashed an airplane into a building, etc., etc.
So, how do people rationalize such a comparison? Well, in my experience, they bring up the Crusades. Nevermind that they took place around 800 to 1000 years ago.
Here are the facts, or maybe my opinions, however you wish to label them: Most Muslims are friendly, live-and-let-live people, with no desire for jihad. For about the last five years, my parents have had a particular Muslim family of Turkish nationality share Thanksgiving and Christmas with them, so I have at least SOME personal experience on which to base this.
There are, however, radicals who desire holy war, and are committing atrocities to satisfy it. They are waging violent war, even against other Muslims. Unlike Christianity, these radical factions have been present almost throughout the history of the religion.
The comparison of radical Islam to ANY Christian group has had no basis for centuries.