I am not a Blues historian, and have not heard enough to speak with authority on the topic. I have been to some of Chicago's most famous venues on the north side, BLUES on Halsted, Chicago Blues, Kingston Mines, and the now defunct BLUES etc... Buddy Guy's Legends, the Checkerboard on the south side and Rosa's on the near west side are also popular spots. Wise Fools Pub on Lincoln Avenue opened back up, but it's not the same as before it first closed.
Blues helps define the Chicago landscape. Every summer in Chicago's Grant Park, Bluesfest brings Chicago's living artform to the masses. Hundreds of thousands will enjoy the day outside and see the bands for free. Yet, local blues artist survive on the cover charge paid at live shows and the cds they sell there. Nationwide record sales are low and there is not much exposure outside of college radio and the occasional hour long shows on progressive FM radio stations.
My favorite party bands are Lil Ed and the Blues Imperials and Phil Guy and the Chicago Machine. Lonnie Brooks, Willie Dixon, Buddy Guy, Otis Rush, Magic Slim, Koko Taylor, and Junior Wells are very good and usually play around town. Big Time Sarah used to tend bar at BLUES and also perform there, but I haven't been in there for a while. Eddy Clearwater 'the Chief' is also a very good performer. I saw him at the old Wise Fools Pub.
Keith Richards jamming at Chicago BLUES