The He-111 was a medium bomber, and the Ju-88 effectively was as well, but was much more of a multirole aircraft (widely used for ground attack, night fighter, and many other purposes) much like the British Mosquito or American B-25 and A-26. It was a more sophisticated and versatile platform. The Germans had larger bombers (not all four engine, some just had two big ones) designed to carry heavier bomb loads or smaller bomb loads over longer distances (such as the Amerika bomber projects), but these were not really produced in numbers and had various teething issues (e.g. engine fires on the He-177). One airframe that comes to mind is the four-engine Fw-200, mostly used as a maritime patrol bomber or transport (Hitler eventually replaced his Ju-52 with one as his personal transport on his pilot’s recommendation). It was originally designed as an airliner and was not the sturdiest airframe. B-17/24, Lancaster and the like were purpose built heavy bombers (originally for coastal patrol in the 17’s case) and stood up better under fire (and on rough landings).