The other, Alvin Plantinga, is frequently regarded (even by Hick) as the most eloquent philosophical defender of exclusivism (that only one faith is correct and others are incorrect) and, indeed, of the rationality of faith in general. He is the John A. O'Brien Professor of Philosophy (Emeritus) at Notre Dame University. His books include Warranted Christian Belief and Science and Religion (w/Daniel Dennett), among many others.
I'll warn you that Hick's talk "Religious Pluralism and Islam" is really quite long, so you may want to break it up. Unfortunately, though many analytic philosophers are capable of stating their case briefly (i.e. 5 propositions or less), they tend not to.
Similarly, Plantinga's "Pluralism: a Defense of Religious Exclusivism" will take a bit of reading as well (note: there's a bio before the main piece; just scroll down). I really recommend both pieces, however, especially because they each account for the position opposite to their own rather interestingly.
Here's a taste of Plantinga:
...in recent years probably more of us western Christians have become aware of the world's religious diversity; we have probably learned more about people of other religious persuasions, and we have to come see more clearly that they display what looks like real piety, devoutness, and spirituality. What is new, perhaps, is a more widespread sympathy for other religions, a tendency to see them as more valuable, as containing more by way of truth, and a new feeling of solidarity with their practitioners.
One is to continue to believe what you have all along believed; you learn about this diversity, but continue to believe, i. e., take to be true, such propositions as (1) and (2) above, consequently taking to be false any beliefs, religious or otherwise, that are incompatible with (1) and (2). Following current practice, I shall call this exclusivism; the exclusivist holds that the tenets or some of the tenets of one religion—Christianity, let's say—are in fact true; he adds, naturally enough, that any propositions, including other religious beliefs, that are incompatible with those tenets are false. Now there is a fairly widespread belief that there is something seriously wrong with exclusivism. It is irrational, or egotistical and unjustified (4) or intellectually arrogant, (5) or elitist, (6) or a manifestation of harmful pride, (7) or even oppressive and imperialistic. (8) The claim is that exclusivism as such is or involves a vice of some sort: it is wrong or deplorable; and it is this claim I want to examine. I propose to argue that exclusivism need not involve either epistemic or moral failure, and that furthermore something like it is wholly unavoidable, given our human condition.
And here's one of Hick:
The historical fact is that we inherit, and always have inherited, our religion together with our language and our culture. And the religion which has formed us from childhood naturally seems to us to be obviously true; it fits us and we fit it as usually none other can. It is true that there are individual conversions from one faith to another, but these are statistically insignificant in comparison with the massive transmission of faith from generation to generation within the same tradition.
How then are we to understand this global situation in which, due to the accident of birth, we all start from within what we have traditionally regarded as the one true faith? To enquire into the relationship between the religions is clearly to ask a difficult but unavoidable question