A good motorcycle GPS is one which according to me should have following features in it.

• Good Build quality to withstand the speeds, dust, and waterproof.
• The company should provide lifetime maps and traffic updates.
• Should have a display of 4 to 7 inches.
• Should provide routes specific to motorcycles.
• Rider Alerts to notify about speed limits, school zones etc.
• Voice based Navigation for much convenience.
• Hands Free Calling when connected to smart phones.
• Should provide latest Point of Interests like Gas Stations, Motels, Restaurants, etc.

These are the one I have looked for when I an searching for a motorcycle GPS for me.