As I noted here, Supreme Court justices have what is, in effect, a lifetime appointment. Therefore, they tend to be any president's most long-standing legacy, in terms of appointments to major offices.
Along those lines, President Obama, in a statement today, said that "there are few responsibilities more serious or consequential than the naming of a Supreme Court Justice". The numbers prove him right.
The longest such legacy, i.e., the longest period between a president's departure from office, and the end of the tenure of his last remaining nominee on the Supreme Court, is that of John Adams. Chief Justice John Marshall died in office, 34 years after Adams left the White House.
Gerald Ford, who holds a record that belonged to Adams for over two centuries, that of being the oldest ex-president, has a chance to surpass Adams's Supreme Court legacy record, as well. If Associate Justice John Paul Stevens, a Ford appointee, remains on the Court until May of 2011, Ford will posthumously win the Supreme Court legacy record. If Stevens survives until then, he will be 91 years old, surpassing the record for the oldest active justice, currently held by Oliver Wendell Holmes, who retired at the age of 90, in 1932.
Eight presidents have had a legacy of 30 years or more (rounded to the nearest year). 21 presidents are beyond the 20-year mark. So, yes, those appointments are certainly consequential.
At the other end of the scale, four presidents never appointed a justice: William H. Harrison, Zachary Taylor, Andrew Johnson and Jimmy Carter. Of those four, Carter was the only one to serve an entire four-year term. However, Johnson was close, having served more than three years and 10 months, when he completed the term during which Abraham Lincoln was assassinated.