I imagine there are plenty of posts on this topic already, but I really struggled to find this information when putting together my own wish list a few years ago. This is a short list of the one commentary I consider the must own for each of the 7 undisputed letters of Paul. Of course if you have the money this list should be widened substantially. My main criteria are: excellent bibliographies/footnotes, new (as they have more up to date bibliographies), a good introduction, in depth exegesis, interaction with Greek, English, and in general the more pages the better. My favorites come from Hermeneia, NIGTC, Anchor Bible, and Word Biblical (WBC). Additionally, I have a strong preference for the format of Hermeneia and NIGTC. This list was made with the help of D.A. Carson’s excellent though succinct work, New Testament Commentary Survey
.
Romans: Jewett – Hereneia: Brand new and massive. This is an excellent resource for Romans.
1 Corinthians: Thiselton – NIGTC: The bibliographies and footnotes are excellent.
2 Corinthians: Martin – WBC: I don’t love this commentary but I haven’t found anything better. Heremeneia you need a 2 Corinthians volume!
Galatians: Longenecker – WBC; Betz – Hermeneia: Okay, Betz’s work may be a bit dated and in some ways flawed but I still enjoy his commentary a great deal.
Philippians: O’Brien – NIGTC; Martin – WBC
1 Thessalonians: Malherbe – Anchor Bible; Wanamaker – NIGTC
Philemon: Barth and Blanke – Eerdmans: A Philemon commentary over 500 pages … you had me at 350.
Feel free to mention any commentaries that fulfill my criteria that you think should supplant the ones I have listed.
Paul of Tarsus 
April 20, 2009 at 6:26 pm
I can’t believe you don’t have FF Bruce’s commentary on Romans listed!
May 31, 2009 at 9:53 am
[…] commentary a 6.5, which is simply unforgivable. I too have provided my insight into which commentary I would purchase for a my personal library if I could only have one from each of Paul’s letters. I will be expanding this entry into a […]
June 1, 2009 at 10:02 pm
We have an article at Paradoseis Journal which is an annotated list of the state of the best technical commentaries in the New Testament. While it is not complete (we are missing a few books) it should be complete soon.
Our criteria is academic and geared for the specialist (not for everyone).
Concerning your fav picks:
(Romans): We consider Fitzmyer (AB) the best, however we listed Jewett (Herm) a close second.
(1 Cor): Fitzmyer (AB) and Thiselton (NIGTC) are a close match in our opinion, Thiselton is more comprehensive while Fitzmyer is closer to our theological conclusions, (Schrage: EKKNT) of course is given due respect, we rank him third.
(2 Cor): It is interesting that you state that you have not found anything better than Martin? Murray Harris (NIGTC) is now the king of 2 Corinthian entries (albeit from a centrist/Protestant perspective), followed closely by the massive entry by Margaret Thrall (ICC). Even Matera (NTL) and Barnett (NICNT) we find as competent supplants for Martin.
(Gal): We have not yet surveyed but J. L. Martyn (AB) immediately comes to mind.
(Philip): Again we have not surveyed but the new release from John Reumann (AB) is the most comprehensive treatment yet.
(1 & 2 Thess): Malherbe (AB) takes the cake.
(Philemon): We like Fitzmyer (AB) the best theologically, while not as comprehensive as Barth (ECC).
_______________________
R. E. Aguirre
Paradoseis Journal