On common Applications, most likely -- most of the speed of the G5 was in the way Altivec was used.
But alas GCC wasn't too big on autovectorization before the switch, so many apps didn't take advantage of it and were G3-compatible applications.
For scientific apps the G5 is a big weapon, for MS Word it isn't.
Integer performance had lagged for years on the PPC until the G5 came out.