There weren’t many original episodes on CBS this week as the network ramped up for May sweeps (which began Thursday, April 28th). Many of the shows that had first-run episodes were either up or down by double digits. The Thursday night line-up — Big Bang Theory, Rules of Engagement, CSI, and The Mentalist — was down and most of the shows hit new season lows.

Which CBS TV shows will be cancelled or renewed depend mostly on the series’s ratings, particularly the 18-49 demographic. Before we get to the season-to-date averages, here are the winners and losers from April 15th through April 21st — based on the coveted demo, as measured against the last original episode.

Week-to-Week Gains: 60 Minutes 1.6/6 (+14.3%), The Amazing Race 2.6/8 (+8.3%), and Survivor: Redemption Island 3.2/9 (+3.2%).

No Change: Mad Love 2.0/5

Week-to-Week Losses: 48 Hours Mystery 1.0/3 (-9.1%), The Big Bang Theory 3.3/10 (-10.8%), Rules of Engagement 2.3/7 (-11.5%), CSI 2.4/6 (-17.2%), and The Mentalist 2.6/7 (-13.3%).

You can see a complete list of the current status of this season’s shows by checking the CBS cancelled/renewed post.

Below is a list of the regular CBS TV shows and their 2010-11 season average ratings to date. It only incorporates the ratings for original episodes and not repeats. The data is sorted by the all-important 18-49 demographic averages. The closer a show is to the bottom, the more likely it is to be cancelled. Fridays and Saturdays are the least-watched nights of TV so those shows get lower numbers.

Raw data: © The Nielsen Company via Media Week.

What do you think? Which TV shows do you think deserve better ratings?

Image courtesy CBS.