Generally I don't think that total hours should be taken as a measure to judge the quality of FOs. Sure, there are some doing an excellent job, while others... -well you know what I mean.
In this case I totally agree with
411A: The key to success are
Proper line training
and
The dedication of the younger pilot to follow directions.
However, while flying for a different airline for a couple of months during 2005, I saw many poor quality CP (with lots of hours), only capable to fly the aircraft, but not having the slightest clue about A/C systems and performance basics.
With other words - poor airmen can be found in both cockpit seats - right and left.
By the way - something else I read concerning flight experience (FO and CPT) and found very interesting:
In a landmark study, Flight Experience and the Likelihood of U.S. Navy Aircraft Mishaps (1992), reasearchers found that "pilots with less than 500 flight hours in model (of aircraft) were at significantly greater ristk for pilot error mishap factors". Interestingly, the study found no correlation between total flight hours and accident rates, indicating that aviators transitioning to new aircraft are at increased risk as well as pilots who are checking out in their first aircraft.