The best robot simulation software?

And which one is the best of them all, there are more, many software here ?
I am need first simulation how an individual servos connected to a microcontroller will behave, which cannot yet be called a robot, and then just a simulation of a finished robot and sensors.
Is there good software for everything up to, and with good tutorials how to use ?

Thanks for this too !
But what of the best to choose?