https://www.kissmetrics.com/ https://mixpanel.com/

These are my favorites. You could also go with something more like http://www.hubspot.com/ if you're not very technical and have money to spend

There's a new event-based analytics tool launching soon - http://www.kilometer.io

Google Analytics - definitely look in-depth at the amount of features available.

Downside to GA is that it doesn't store personally identifiable information, so if you want to track and interact with users at the individual level, you will have to create a unique identifier in GA and then export it and match it to your user database.