Is Stock Market better than other investment instruments for retirement planning ? or is it just a hype ?

The Indian companies (most of) does not encourage innovation like US, makes it less attractive for investors worldwide. Looking the past few years data, FIIs have been net sellers and it increases YOY. If this continues then the market would just be able to match inflation in the best case. What is that thing which makes people believe that it is better instrument for retirement planning ?