I was mildly rebuked by a good friend for suggesting that Christians of Protestant belief were practicing Traditional Christianity. My friend suggested that Eastern Orthodox and Roman Catholic Christianity was Traditional and that Protestants practice of Christianity is non-traditional.

I was curious when reading his thoughts and frankly, I'm still wondering? What is Traditional Christianity and are Christian Protestants practicing it? 

Let me state a bias up-front.  I generally think any statement that says "Protestants believe..." or "Protestants do...." is inaccurate.  There is much variation among denominations.

For me, "traditional christianity" includes the denominations that claim the Apostles' and/or Nicene creed as general statements of faith.  This would include Catholics and well as Anglicans/Episcopalians, and the reformation churches (Lutheran, Methodist, etc).  In general, they have pretty similar liturgies, most believe in the Real Presence in the eucharist/communion, and more-or-less share a litugical calendar and a lectionary that provides for broad coverage of the Bible on a cyclical basis.

WorldCitizen, my response regarding lumping  protestants together was inspired by the original post.  It was not in response to your observations. 

Coming from a heavily Evangelical background...

it honestly depends on the speaker. Obviously an Academic, as well as a member of any Catholic or Orthodox church, would consider Orthodoxy and any rite of Catholicism as "traditional."

However, Evangelicals have so many different opinions. My grandparents are Evangelical, but they are also strict Lutherans. They don't agree with a lot of Catholic doctrine (obviously), but would consider it "Traditional." But they're also older, and the older generations would think any High Church Christianity is "Traditional." I have a friend who attends an Evangelical, Non-denom Church that advertises itself as "Non-traditional." And many of these Evangelical churches define "Tradition" as hymnals, a quiet service focused on a sermon from a pulpit, and wearing formal attire to Church.  Many of them also seem to be avoiding the word "Church" these days.

 But there's also the matter of whether or not "Traditional" = "Right." For example, I know an Evangelical that would lump the two terms into the same meaning, which means Mormons and JWs aren't "traditional."

I think, within Low-Church Protestantism, there's a common notion that "Traditional" Christianity is any Christianity that believes in "the Bible, the Trinity, and Jesus's death and resurrection." There are those that picture Catholic and Orthodox theology as not being any different from their own, both out of genuine ignorance of those Churches as well as a desire to show the non-Christian world that all Christians think alike.

From an Evangelical perspective, it's kind of hard to answer, both because it depends on what you're trying to accomplish in labeling something "Traditional" and because "Tradition" has different meanings to different Evangelicals.