I waffle back and forth on the need for commentaries.  Commentaries are an excellent way to help teach Bible Studies on a particular book.  Rarely do I consult a commentary for preaching.  I’m not against commentaries.  I just don’t use them.

I recall Dr. David P. Scaer once showing students in the CTSFW bookstore what commentaries to buy for the Gospels.  His recommendations were:

Matthew: International Critical Commentary Series by W.D. Davies and Dale Allison, Jr.  3 volumes.  Now available in paperback.  Very pricey set in hardcover.

Mark: Anchor Bible Commentary by C.S. Mann.

Luke: CPH Commentary by A.A. Just, Jr.  2 Volumes.  I recall the Anchor Bible Commentary by Joseph Fitzmyer  being recommended by someone somewhere.

John: Anchor Bible Commentary by Raymond Brown.  2 Volumes.

Mind you, this was close to ten years ago.  Numerous commentaries have been published since then.  His recommendations may have changed.

Wisconsin Lutheran Seminary has an updated list of what they recommend for commentaries in Old and New Testaments.