Are mobile emulators/simulators good enough to test websites on mobile browsers?

It is recommended to test on physical devices instead of simulators for real world test results. 

The iOS Simulator OR Android emulator is a great tool for rapid prototyping and development of your app. However, it is important to test your app on physical devices as a simulator/emulator and a physical device differ in hardware, API support, framework support & OS features.
Learn more about Emulators vs Simulators vs Real devices here.