The PowerPC G3 and G4 were great chips. The G3 was much better than competing x86 chips, and G4 beat contemporary ones consistently too.
The G5 wasn't great though. When Steve Jobs announced it, Apple already showed it only trading blows with the then-current Pentium 4 (a Pentium 4 - they sucked!). And a few months after the first Power Mac G5s were launched, they were already resoundly beaten by the new Athlon 64s [1].
Add to that the G5 was basically a POWER4 server chip, and IBM was only building server chips in the future, Apple basically had no choice. Nothing really to do with PowerPC vs x86, but more to do with what kind of processors their suppliers were willing to build.
The G5 wasn't great though. When Steve Jobs announced it, Apple already showed it only trading blows with the then-current Pentium 4 (a Pentium 4 - they sucked!). And a few months after the first Power Mac G5s were launched, they were already resoundly beaten by the new Athlon 64s [1].
Add to that the G5 was basically a POWER4 server chip, and IBM was only building server chips in the future, Apple basically had no choice. Nothing really to do with PowerPC vs x86, but more to do with what kind of processors their suppliers were willing to build.
[1]: https://web.archive.org/web/20050605023250/https://www.pcwor...