I can't estimate, but most probably I played both PSI and PSIII more than 10 times and PSII 5 times (counting only the times that I finished the games). PSIV I've played 2 or 3 times to completion, but as it is by far the worst, I don't wan't to play it so often.
I've also played the Gaiden, Adventure and PSII Text at least once each.