An excellent example of that is Alicante Bouschet. A second tier grape in France, brought by the Reynolds family to the Alentejo (likely because of its generous yields at a time when viticulture was being revived, post-phylloxera) where it was found to produce phenomenal, age worthy wines. It remains the most important red grape there.
So true, but Tomas you knew I was already a fan.
For everyone else, try a 30-40 year old Herdade do Mouchao. As great a wine as anywhere.
Reading this thread, how much of being a “first-tier” grape has to do with how adaptable the grape variety is. Cabernet Sauvignon and Chardonnay are grown extremely well in lots of places. Pinot Noir and Riesling can be grown well in fewer spots (need cooler climates) but reach tremendous heights for a number of wineries in spots where they grow well.
By contrast, Grenache is grown very, very widely in many wine regions but probably in only a handful of places are great wines (like Rayas) made from it.
Note that while I find this an interesting way to look at the above discussion, I agree with those who have said that they abhor the notion of a few “noble varieties.” I really don’t like the trend in the world of wine of more and more regions growing fewer and fewer “international” varieties and getting away from their historic roots. For me, focusing just on variety means that there will be an ocean of mediocre wine from that grape type. Rather, matching grape variety to soil and climate is a key to making great wine from a variety. It would be tragic to see Cabernet Sauvignon grown in Barolo or Taurasi, for example, or to see Syrah replace Grenache in CdP.
Wow, you are so good at spelling!
Teroldego
As others have noted, the original list was French Noble Grapes, really. Now that we see the world of wine more broadly there have to be many candidates from other countries, not least Italy. To be fair, decades ago there were very few examples being made of some of the obvious Italian candidates for a new list; the first famous Aglianico was made in the late '60s, for example.
That’s exactly right Oliver. And there were places that had grown grapes for centuries but in the aftermath of two world wars were relegated to nearly forgotten status. And to the point Wes made, nobody, even the greatest wine makers, were able to see much beyond Europe and the possibility of wine in the US and Australia. In the past few decades, Chile has become home of some wonderful wines. And places like China? Who knows what kind of potential there is. Italy has more grape varieties and has been making wine longer than France, and yet the list is limited to France. The concept of “noble” grapes came out at a particular moment under specific circumstances that have utterly changed, and it’s a useless term today.
My understanding of Noble Grapes is historically they are considered overall the highest quality grapes with the ability to grow well in most winemaking areas of the world (outliers aside), making them the most prolific on a global scale, which are:
Cabernet Sauvignon
Merlot
Pinot Noir
Sauvignon Blanc
Chardonnay
Riesling
My personal opinion is all grapes, noble or not, can be made into amazing wines, in the right vineyard, with the right growing conditions, with the right vigneron and the right winemaker. And there are many, many examples of the opposite, which the noble grapes are being made into terrible wines.
So I see it as 2 separate concepts:
1.)What are the most versatile grapes, which have the broadest appeal globally, not just in an isolated country/area
2.)What grapes go into what are considered the greatest wines of the world, that historically may not grow well everywhere, but where they do grow well, they are the highest quality grapes going into the top tier wines, therefore should be considered a “noble grape”, which I think is the point of the OP.
Just one girl’s opinion 
No, there are great rousanne/marsanne wines made all the time. Try Bernard Faurie’s Hermitage blanc from 2000 and tell me if that is not ‘great’.
Nerello Mascalese and Carricante will, quite rightfully, be elevated to DOCG status. It’s inevitable.
I think the elevation to DOCG is largely political, or at any rate not inspired by objective quality. The first white wine type to receive the distinction was Albana di Romagna, for example.
Which do you think are the top producers?