Being in the audience of the Chicago premiere of “Louis & Keely ‘Live’ at the Sahara,” at the Royal George Theatre, 1641 N. Halsted St., felt much like being on the Strip in Las Vegas. Not today’s Vegas with its flashing lights, exploding fountains and sidewalks so crowded that you can hardly walk from one of the 65 majestic hotels to the next. No, it seemed more like the Las Vegas I experienced on my first visit in the 1950s when hotels such as the original Flamingo, Thunderbird …