Favourites:
Billy Connolly - great joke and story teller, a real natural gift for making things funny with a touch of surrealism. One of those people that would make a party great if he was present.
David Mitchell - Some see him as a bit of a snob (why, I don't know), but I think he's a brilliantly angry man, angry and frustrated for all the right reasons, and delivers it intelligently, and precisely.
Richard Pryor - Like Connolly, makes any story funny and has an uncanny knack for picking out the funny things in tragic circumstances.
George Carlin - I actually don't laugh so much at Carlin when I watch his old performances, rather I just sit and agree with him. No bullsh*t whatsoever, you'd have a hard time pulling the wool over his eyes.
Rowan Atkinson - His old stage act was superb, making use of his incredible ability to express and move. He could read the shipping forecast in front of a camera and probably make me crease up.
Least favourites:
Lee Evans - Just never found him funny, he has incredible energy but reminds me of a kid with ADHD rather than a comedian.
Michael McIntyre - Someone mentioned "stadium comedy", and I agree. Jack Dee has gone a little down this route too, but McIntyre is one of those "standby" comedians that can compere a big arena. The jokes feel mass produced and obvious with no real personal injection of humour.
Alan Carr - Just annoying. Camp comedy is hilarious if pulled off properly (q.v. Larry Grayson), Carr misses the mark for me.
Middle ground comedians (normally mean they started well, but now have gone down a bit in my estimation):
Peter Kay: Hit the nation head on, with an incredibly accurate and comic view of life, which a lot of working class people certainly identified with. A lot of his stand up flowed into his TV series, and a lot of the jokes were easily traced. Disappeared off the radar a little bit now, and I think he's used up most of his experience from which to draw material from.
Jason Manford: First thing I though was "doesn't he sound like Peter Kay?" but proved himself to be quite funny and concise. Seems to be heading down the McIntyre route though.
John Bishop: See above, minus the Peter Kay comment.