Alex Ross has given a list of classical CDs that would be good for starting a collection. He has several caveats at the beginning, which I will try to obey while picking a major nit. One of his caveats is that he picked cheaper recordings, so that all 10 would cost only about $150. This is a good criterion, as long as it isn't used to justify really crappy recordings. He also makes clear that this isn't a best recordings of all time list, or a must have list, just a good list for getting started. Fair enough.
But please, not the Gilbert Kaplan recording of Mahler's Second Symphony! For those that don't know, Gilbert Kaplan is an investment banker who developed a passion for Mahler, specifically his Second Symphony. Kaplan has never studied conducting or musicology seriously, but tries to apply both disciplines in his performances of Mahler. His recording comes with copious letters, notes, and justifications for his choices of bells, antiphonal brass choirs, etc, that show a well-meaning yet poorly trained musician. Kaplan's recording with the London Symphony was the first exposure I had to Mahler's Second, and I immediately hated it. I figured for a long time that this was just a bad symphony, not on par with his Third and Fifth symphonies (the others that I knew). Finally, when preparing for an orchestral audition that called for several excerpts from the Second, I borrowed some other recordings, including Simon Rattle's beautiful rendition. I found out that the Second was not the musical equivalent of an angst-ridden, hormone-crazed teenager, but had true beauty and substance.
Maybe Alex recommended this CD because it comes with a score, and does include some interesting background about the symphony. But I don't think that can justify picking such a naive performance over many other lovely interpretations.