The G5 was one of the ones I was looking at.  As always, Canon makes a great camera (I also have a Canon S400, A50 and ZR40 DV cam.).  The G5 is a different class of camera than the A1 with a smaller focal range of 35 - 140mm, smaller CCD, slower AF, slower shutter speeds. no IS, live histogram etc.  On the positive side, it is smaller, has a bright f2.0 lens, fully articulated LCD, costs less.
It depends on what you want.  There are a ton of different cameras with different features and price points to suit each persons needs.  To me. the extra ~ $100 for the A1 over the G5 was a no brainer.  Two different classes of cameras.
What are important features for you?
Focal length (wide)
Focal length (tele)
low light 
sports/action
macro
size/weight
cost
AF speed
flash internal/external hot shoe
cost
Handling (it has to feel right in your hands and be comfortable to use)
Easy point and shoot auto
lots of manual control
etc.......