There was no stopping Zidane's men in the opening stages and James piled even more misery on Espanyol when his 16th-minute shot took a deflection off Papa Kouly Diop before finding the net.  
Benzema could have made it four shortly after following an intelligent one-two with Isco, but he aimed just wide from eight yards out.  
Espanyol got their first chance of note shortly before the half-time whistle after a quick break involving Mamadou Sylla and Salva Sevilla, but the latter's attempt was too weak to worry Keylor Navas.  
Ronaldo was not to be denied in the dying seconds of the first half, however, dancing past three opponents before beating Arlauskis with a powerful left-footed shot.
Benzema should have made it five at the hour mark after some good work from Ronaldo down the right, but the striker's header lacked the power and accuracy to worry Arlauskis.
Ronaldo handed the former Lyon man another gilt-edged chance after a good combination with Marcelo down the left, but Benzema once more failed to get his attempt on target.
Madrid kept on pushing for more and Ronaldo nearly got his hat-trick when he lifted a free-kick over the wall, only to see his attempt clip the top of the net.
Ronaldo eventually made it 5-0 in the 82nd minute with his 19th Liga goal of the season to draw level in the Pichichi standings with Luis Suarez. He headed home from close range after a fine cross from Jese, before Espanyol debutant Oscar Duarte beat his own goalkeeper to cap a dominant outing for the hosts.