Why is SAP better than other ERP solutions?

It is not necessarily better. 

All ERP packages have their strengths and weaknesses. SAP's weakness is that it is very expensive and takes a long time to implement. SAP's strength lies in the ability to develop and customize  - to handle complex business processes that other software doesn't 'fit'- and you can find a thousand Oracle proponents who will claim they can handle the same complex requirement - and they're right. 

The market penetration revolves around client size. If you have 5 customer service reps processing returns, well, Sage ERP has a half a dozen packages that will handle that. However, if you have 500 customer service reps you can use SAP and shave 60 seconds off the time it takes to complete the task with Sage, that's 500 x 60 seconds x 25 transactions per day x 5 days a week x 52 weeks a year x $15 per hour, it's close to a million a year in labor savings. And that's just in customer service. Factor in similar efficiencies in warehousing, delivery, web services, finance, and so on, and suddenly the $5m to install SAP makes sense - even the $3m to upgrade gets approved.  But none of it makes sense until you are in a company large enough to have, say 500 customer service reps worldwide.

SAP is most powerful but it is very expensive as compare to ERP as well it take more time to implement because of its vast modules but once it is implemented then it take of the work of the big organization because small company can't afford SAP package of ERP solutions However it is best enough in its reliability and effective.