Judaism distinguishes between obligations of the Jewish covenant at Sinai and obligations under the Noahide covenant (for the other nations).
Under the covenant of Sinai it is stated explicitly that worshiping any created being as a manifestation or incarnation of God is idolatrous.
However - in the case of the other nations, any religion that believes that there is a single supernal supreme being, whether or not they believe it incarnated or manifested as a created being is not considered idolatrous.
Thus, under the Jewish definitions, Hinduism and Christianity are not idolatrous for non-Jews but are idolatries if Jews hold similar beliefs.
cf. Deuteronomy 4:15 - 19
laws of Avodah Zarah