Alright, Protestants, three questions:
1) Who compiled the New Testament of Scripture as you have it now?
2) Do the contents of Scripture yield obvious truths revealed by God or are they liable to misinterpretation?
3) Is your interpretation of Scripture infallible?
1) Who compiled the New Testament of Scripture as you have it now?
Jewish rabbis for the OT and the Apostles for the New.
Look, ignoring the fact that the modern-day RCC is a far-cry from the ante-Nicean Church, claiming that compiling a list of authoritative Scriptures gives you a special authority over them would be like me compiling a list of great classical musicians and claiming that I was greater than them. The Scriptures canonize themselves by virtue of their annointing by the Holy Spirit, not by virtue of being ratified by a later heirarchal body.
2) Do the contents of Scripture yield obvious truths revealed by God or are they liable to misinterpretation?
Yes. The Bible is, as one commentator put it, "waters shallow enough that a child can play in it, but deep enough that an elephant can immerse in it." Frankly, on most of the issues that divide us, the Bible is quite clear and you're forced to rely on out-of-context quotations and on placing tradition over the Scriptures.
Granted, there are a number of places where the Scriptures are obscure enough that honest theologians will doubtless disagree until Christ returns to explain them personally. In some cases, we're arguing about shades of meaning; in others, one side or the other is dodging the plain and natural interpretation in favor of one more comfortable to them or one that they were taught.
But either way, in regards to the issues of salvation, the nature of the Church, works vs. faith, Christ (not Peter) being the Rock, etc., the passages involved are extremely plain in their meaning, so much so that the Catholic is often reduced to simply dismissing the messenger rather than discussing the text.
3) Is your interpretation of Scripture infallible?
On every single point? I doubt it. Neither is yours, or the pope's, or tradition's. The goal is to continually grow in our understanding of the Scriptures, and through them, to know God better--not to simply accept some other authority's word on the matter.
"Do not call anyone on earth your father; for One is your Father who is in heaven. And do not be called teachers (rabbis); for One is your Teacher, the Christ" (Mt. 23:9-10).
Many Catholics like to get around the obvious injunction in the above by saying, "What do you call your earthly father?" That's not the point. The point Jesus was making was not to put anyone between you and Him as some kind of master interpreter or intermediary.