I've had some time lately to listen to my Mahlers on my Zune. I decided to revise my previous posting to this thread from last December on re-exploring Mahler to the following (additions are in bold):
M1 - de Waart/Minnesota, Honeck/PSO
M2 - Blomstedt/SFO, Jansons/Oslo
M3 - Zinman/Tonhalle, Salonen/LAPO
M4 - Chailly/RCO, Levi/ASO, Vonk/SLSO
M5 - Shipway/RPO, Abbado/CSO (Dale Clevenger is rock-solid in the Scherzo)
M6 - Farberman/LSO, Boulez/VPO, Mackerras/BBC Phil
M7 - Halász/Polish NRSO, Bertini/Köln, Barenboim/Berliner Staats.
M8 - Wit/Warsaw, Bertini/Köln, Gergiev/LSO
M9 - Giulini/CSO, Sinopoli/Philharmonia, Mund/KSO
M10 - Chailly/Berlin RSO, Harding/VPO
The Welte-Mignon Piano Rolls - Mahler on recording piano
Although originally offered as a list of alternatives, I suppose this really is becoming my A-list.
Some of my new entries, e.g. M1 & M8, were released within the last year so I confess that technically they can't be re-exploring candidates.
Some new-to-me acquisitions e.g. M4 & M7, compelled me to displace some fine predecessors.
However, some of my old stand-bys, e.g. Salonen's M3, Abbado's CSO/M5 & Mackerras' M6, have insistently restored their favor.
In some cases, e.g. M1, M8, M9, and M10, my new acquaintances were instantly appealing additions.
Lastly, though I have Eschenbach's M2 (& Mehta/VPO, Bertini, Zinman, etc.), I haven't been motivated to revise the Blomstedt & Jansons entries. Each has its a shortcoming, but overall they remain convincing to me.