Regarding the G lens, you are correct in that newer Nikon camera bodies require one leaves a lens that has an aperture ring set to the minimum aperture anyway to the ring seems superfluous. You have to understand, however, that there are many many Nikon owners still using bodies that are up to decades old - one of Nikon's attributes has always been the high quality and longevity of their gear. It is those folks who whine about the lack of an aperture ring - as their older cameras don't have the ability to control aperture from a "command dial".
Now, along the way, Nikon has made some G type lenses in so-called "consumer" quality as well as "pro" quality. For ex&le, the 70-300 G you mentioned is a relatively inexpensive lens (usually about US$100). Nikon has a D version 70-300 with ED glass that by all accounts is much better optically (same aperture range). So the theory goes that the G lens is cheaper to make it more affordable.
However, Nikon's 70-200 f2.8 AFS VR lens is also a G type - and it's in the US$1500+ price range, clearly aimed for pros. Optically it is apparently quite excellent, following its predecessor the 80-200 f2.8 AFS.
So, for owners of new Nikon bodies, G lenses are fine as far as usability goes. Each G type lens should be reviewed independantly, though, as some are built to a higher standard than others.
Hope this helps,
BobF
PS: Am I the only one who finds this list annoying in that one cannot see the preceding thread when reading a response?