there is a big gap between the popularity of IPL and PSL. PSL is still very fresh and has a long way to go.
PSL need more time to get popular and if you make comparison with IPL then they have to go a long way to match that level. After big bash league IPL has been the most popular cricket league and worldwide cricket fans eagerly wait to enjoy this league. Its just not only like that IPL got strong support from BCCI but also indian bollywood community gave tremendous support which bring massive popularity in a short time. I haven't seen this type of celebrity and business tycoons involvement in other cricket leagues. Even their football leagues are also getting popular day by day and have same support source.
Due to Pakistan's terrorist attack on Srilanka cricket team ICC put restrictions on hosting cricket matches and it was a really bad time for PCB. After this few years later with the support of their government Pakistan cricket board managed to run cricket matches again and as a result PSL launched. So in a situation like this its need more time and hopefully they will be able to get best players on their league in upcoming seasons.
Right now IPL is just like EPL which is world's best soccer league and after this we have some good leagues in Europe same happening in cricket IPL, BBL and Vitalty Blast then we can talk about PSL but if we have some good seasons in Pakistan then surely this can increase in ranking even not near to IPL but surely could be good and popular league in future for good and quality cricket.