Capacitors have many properties and there are many tests that can be used to determine their well being. ESR is but one type of test to measure one property. Others may include, but are not limited to, capacitance, leakage, and Q factor. Take a peek at the data sheet for several types of capacitors and you'll see what I mean.
So, just because two capacitors have the same ESR doesn't necessarily mean they're equally good or bad. There may be other problems that aren't detected by an ESR measurement. However, if you didn't have an ESR meter, then you'd have even less information available to make a determination.