Recently I found this interesting device Art-O-Meter:
Art-O-Meter is a device that measures the quality of an art piece. It bases its evaluation on the amount of time that people spend in front of an artwork compared to the total time of exhibition. The measurements are graphically represented by comments and a 5 star rating system.
This device may help you to evaluate of artworks. But IMHO it’s very very visual. And it might be more reasonable to read some information and opinions before visit of art gallery.