I live in Mumbai -- while the commuter trains have lots of room for improvement, they do run at ~3 minute headway for most of the day, and that's on tracks shared with the national rail network. I'd expect a metro system with its own dedicated tracks to be able to do even better, at least at peak hours.

Just to be clear, I'm not complaining -- 5 minutes is pretty great, and the Mumbai Metro system (separate from the commuter trains) is also worse at about ~6 minutes -- but even so, I was hoping this system might be able to achieve times like the Paris or Moscow Metro