Sheared granular suspensions can either flow or be jammed. They show as well a 'melting' transition: partially ordered flowing states are found which can be melted into fully disordered arrangements of grains by sufficient shear. While these are well documented phenomena, the underlying mechanisms and their control parameters are still far from clear. Via Molecular Dynamics simulations, we study the rheology of a model system of sheared frictional monodisperse granular materials [7,8]. In particular, we aim to understand the nature of a critical line separating crystallised and melted states and the "jammed" region in the phase diagram. We outline as well connections and differences with thermal glass formers and colloidal suspensions.