Rishonim
Maimonides strongly put forth the view that Muslims were not idolaters. Although, to be sure, Islam was heresy,[18] this did not stop Maimonides from expressing a positive view about Islam - or even about Christianity, which he considered to be idolatry.[19] He ruled that although Islam and Christianity are both in error, they still have some value in that they prepare the world eventually to accept the sovereignty of G-d[20]
In Maimonides' system there was one point on which Christianity, although idolatrous, actually stood above Islam. The Talmud states that it is forbidden to teach Torah to non-Jews, and this interdiction is clasified as halacha by Maimonides. However, he makes an exception for Christians, because they believe in the same text of the Bible as the Jews and it is thus possible that, after having studied, they will recognize the error of their ways. For Muslims, however, because they do not accept that the five books of Moses are Divine, such a possibility is not to be considered. It is, therefore, forbidden to teach them Torah.[21]
However from this ruling, one can conclude nothing about the basic worth of Christianity vis-a-vis Islam. The prohibition to teach Torah to Muslims was due to the specific reason cited, and did not speak to any of the broader issues involved in evaluating their religion. In appears that it is Islam that was more favorable in Maimonides' eyes. As we have seen, according to him, both Christianity and Islam have a positive role to play in the world. However, with regard to Islam, despite certain critical comments regarding Muhammed,[22] the fact that Islam is not idolatry creates a crucial distinction between it and Christianity and leads to numerous consequences, both in law and theology. David Novak argues that this explains Malmonides' belief that Muslims, as sons of Ishmael, are required to circumcize their sons.[23] Maimonides rules that although a Jew may not obtain benefit from wine handled by a Christian, that is not the case with regard to a Muslim. However, Maimonides does agree with the view of the Geonim that it is still not permissible to drink this wine. According to Maimonides, this ruling was supported by "all the Geonim"[24] According to R. Asher of Montanzon[25] Maimonides saw the works of "all the Geonim." The Radbaz was of the same opinion [26] However, it is not clear that this really means "all" as there were Geonim who do not agree with this position[27], Nahmanides says that "some Geonim" agree with the law as codified by Maimonides.[28] and, as we have already noted, this stringency had nothing to do with Islam as a religion but was to prevent socialization with non-Jews generally.
http://en.wikinoah.org/index.php/Islam_and_Noahide_Law