The G4 was where the rot started to set in, but people are forgetting about the 601, 603 and 604, which had themselves several years of history in Apple designs. The 604 in particular was a real piledriver for some applications and easily competed with x86 of the same era, and the G3's integer performance was even better (its main Achilles heel was a fairly weak FPU, but this wasn't a major issue at the time for its typical applications).