How to compare Christian pastor credentials? Requirements for ordination vary across denominations. Baptists and Pentecostals, for example, will ordain people without even a high school diploma, whereas many of the more liturgical denominations require masters and doctoral level degrees before one can even preach.  

How then, is one able to assess the academic qualifications of ordained clergy across denominations?  In other words, is there a resource that would assist one in gauging the stringency of the qualification process before one is allowed to serve as preist, minister, or pastor? And, what common requirements for ordination can be compared across denominations, so as to be able to compare similiar qualifications across denominational lines.
The kind of comparison you are suggesting is not going to work for a number of reasons. The most prominent one is a huge difference in job description between those that different denominations consider church leaders.
The Catholic church, for example, ordains priests based on several years of college-level education, as well as other requirements, academic and spiritual. However they often select leaders who do not have any formal education and give them the education required to do the job. Moreover a Catholic church will typically have one priest overseeing a church with many hundreds of members. Various other paid and volunteer workers take on other roles within the church.
A Baptist or other Protestant church of similar size may have several people with the title 'Pastor' on their paid staff. Those people may have different responsibilities. There may be a children's pastor, a music pastor, or even an administrative pastor. There may be an outreach pastor whose job is to work with the homeless and street people. Many of those people are qualified very differently from the Catholic priest, and any attempt to draw conclusions by comparing their qualifications is not going to yield useful results.
Even if you were to compare just 'lead pastors' (those in charge of an entire congregation), just because a denomination has no minimum standard of academic qualification doesn't mean they habitually appoint those with no academic qualifications. Most of the churches I know that have no minimum standards routinely appoint people with masters degrees.
Another significant issue is the one of who appoints church leaders. Catholic, Anglican and many more 'high church' denominations have their leaders appointed (ordained) by the denomination. This means a certain amount of uniformity of their leaders. However in congregationalist denomination each church appoints its own leaders. This means leadership qualifications are decided by every single church. There might be different standards for every single Baptist church in a denomination, as well as between denominations. Not to mention that each church is free to revise its own standards or ignore them if it feels like it.
As another aside, I don't know of any denomination that requires a masters degree - or any degree - before they are accepted for ordination training.