What makes a quality leather jacket?  Good question and an important one.  You should look for a couple of basics such as a YKK zipper, 3M Thinsulate, and a decent warranty period. 

A jacket with these basics means the manufacturer is not trying to cheap out on you the consumer.  In addtion to these basics you want to look for double stitching and drum dyed leather. 

A high quality jacket should be symetrical in cut and fit.  The leather should be basically consistent in appearance and made from as few cuts of leather sewn together as possible.