Using regular season W-L pct. as a measuring stick, the 2000s are just percentage points away from being the second best decade in Cardinals history. Here are the six best: 

1. 1940s  .623 (960-580)

2. 1930s  .56649 (869-665)

3. 2000s  .56619 (911-698)*

4. 1960s  .552 (884-718)

5. 1920s .536 (821-712)

6. 1980s  .529 (825-734)

* 10 games remaining

If I'm calculating correctly, in order for the 2000s Cardinals to move into 2nd place they need to go 7-3 for the remainder of the season. This would give them a W-L pct. of exactly .567 for the decade. Pretty impressive, given the illustrious history of this franchise.