The strength of the electromagnet depends directly on the current (amps) in the wire that the coil is made out of. That current is going to be determined by the voltage of the battery or power supply that powers the magnet, and by the resistance of the wire. So yes, the properties of the wire do have a direct effect on the strength of the magnet. If you tried to make an electromagnet with a coil of wet spaghetti, it would work, but you would need a humongous power supply to get any significant strength out of the magnet.
