Vertical metal-insulator-graphene (MIG) diodes for radio frequency (RF) power detection are realized using a scalable approach based on graphene grown by chemical vapor deposition and TiO2 as barrier material. The temperature dependent current flow through the diode can be described by thermionic emission theory taking into account a bias induced barrier lowering at the graphene TiO2 interface. The diodes show excellent figures of merit for static operation, including high on-current density of up to 28 A cm-2, high asymmetry of up to 520, strong maximum nonlinearity of up to 15, and large maximum responsivity of up to 26 V-1, outperforming state-of-the-art metal-insulator-metal and MIG diodes. RF power detection based on MIG diodes is demonstrated, showing a responsivity of 2.8 V W-1 at 2.4 GHz and 1.1 V W-1 at 49.4 GHz.