Yisro, upon being informed of the great things Hashem did for the Jews, says (Shemot 18:10-11):
There is in fact a dispute between two of the Targumim. Tg Yonatan translates the phrase in question straightly.
כדון חכימת ארום תקיף הוא ה על כל אלהיא
Though Tg Yonatan is typically more expansive and brings in more midrashim, for this phrase it does not. (It does, however, bring down the understanding of the remainder of the pasuk as referring to Hashem's greatness in punishing middah kineged middah.)
Tg Onkelos, in contrast, says כען ידענא ארי רב ה ולית אלה בר מיניה, which means "Now I know that Hashem is great/mighty, AND there is no god except for Him." This is not exactly the literal translation, but Onkelos, which adds extra words to avoid assigning anthropomorhism to God, could be expected to do the same here.
This is not to say that Onkelos is incorrect. In fact, one could read עַתָּה יָדַעְתִּי, כִּי-גָדוֹל ה מִכָּל-הָאֱלֹהִים ,כִּי בַדָּבָר, אֲשֶׁר זָדוּ עֲלֵיהֶם as follows: Now I know that Hashem is greater than all of the others purported to be gods, in that they (the Egyptians) tried to harm them [and Hashem prevented this from happening as mentioned in the previous pasuk].
In other words הָאֱלֹהִים refer to all who are regarded to be gods, and Hashem is greater because He actually has power.
Indeed, we see a close approximation to this in Tehillim 96:4-5: (and Divrei Hayamim 1 17:25)
Tg Onkelos, though, takes an extra step of dividing the phrase in two. First: for Hashem is great. It is not a measure compared to anything else - not "greater than X." That is a translation of עַתָּה יָדַעְתִּי, כִּי-גָדוֹל ה. Second: "AND there is no god except for Him" which translates מִכָּל-הָאֱלֹהִים, as "He exists, of all the gods." It is a slightly midrashic type of parsing, which is not really necessary in this case.