E4>E2>E1>E3.
E4 is challenging and fun to play. The problem with The Shores of Hell is E2M3 (very flat and boring, though the room with slime, pillars and lost souls has inspired some other mappers) and the secret map. E1 will never be my favourite with such a limited monster roster and no plasma weapons. E3 has plenty of sub par maps, E3M1, E3M2, E3M8 and E3M9.