In 30+ years of ETOPS there has never been an accident. 

ETOPS aircraft have much higher maintenance and safety regiments than non-ETOPS. 

Nearly every time a 4 engine aircraft loses an engine it will also divert. BA learned this lesson when one of their 747s had to make an emergency landing before it almost made it to LHR. The pilot lost an engine much earlier in the flight but decided to continue. Because of weather he damn near ran out of fuel before declaring an emergency and landing short of LHR. 

The vast majority of trans-ocean flights these days are in twin ETOPS. 

Using your logic that 4 has to be safer than 2, we should insist that 6 engine aircraft be in the flight line.