A better question would be how well has the aircraft and engines been maintained over their lifetime. A poorly maintained 2 year old aircraft is far worse than a well maintained 30 year old aircraft.

You might also ask how good are the flight crew considering that many accidents are resulting from actions or inaction by them, rather than any factor relating to aircraft age. Would you rather fly on a 30 year aircraft with BA, or a 5 year old aircraft with PIA?