Early translators of Akkadian believed that the ideogram for the god called in Sumerian Enlil was to be read as Bel in Akkadian. This is now known to be incorrect; but one finds Bel used in referring to Enlil in older translations and discussions.
Bel became especially used of the Babylonian god Marduk and when found in Assyrian and neo-Babylonian personal names or mentioned in inscriptions in a Mesopotamian context it can usually be taken as referring to Marduk and no other god. Similarly Belit without some disambiguation mostly refers to Bel Marduk's spouse Sarpanit. However Marduk's mother, the Sumerian goddess called Ninhursag, Damkina, Ninmah and other names in Sumerian, was often known as Belit-ili 'Lady of the Gods' in Akkadian.
Of course other gods called "Lord" could be and sometimes were identified totally or in part with Bel Marduk. The god Malak-bel of Palmyra is an example, though in the later period from which most of our information comes he seems to have become very much a sun god which Marduk was not.
Similarly Zeus Belus mentioned by Sanchuniathon as born to Cronus/El in Peraea is certainly most unlikely to be Marduk.
W. H. D. Rouse in 1940 wrote an ironic end note to Book 40 of his edition of Nonnus' Dionysiaca about a very syncretistic hymn sung by Dionysus to Tyrian Heracles, that is, to Ba‘al Melqart whom Dionysus identifies with Belus on the Euphrates (who should be Marduk!) and as a sun god:
... the Greeks were as firmly convinced as many modern Bible-readers that the Semites, or the Orientals generally, worshipped a god called Baal or Bel, the truth of course being that ba'al is a Semitic word for lord or master, and so applies to a multitude of gods. This "Bel," then, being an important deity, must be the sun, the more so as some of the gods bearing that title may have been really solar.Bel is named in the Bible at Isaiah 46:1 and Jeremiah 50:2 and 51:44.