He is a terrible actor, his performances in Arthur and St.Trinian's highlights this.
Never listened to his Radio show.
As far as his comedy routine goes... It's genius to blithering idiots yes, but I was raised on George Carlin, Sam Kinison and Bill Hicks and Brand to them would be like comparing a Ford Fiesta to a Mercedes A Class.
Well I've never heard of any of those three, so I can't compare them. Are they American? I rarely find American humour funny, and as a result don't really know the names of most of the USA comedians.
But if you actually listen to Russell's comedy, it is very clever. I don't think "blithering idiots" would understand some of the vocabulary involved for a start.