I have never had an experience with a G40 or R40, and only limited experience with IBM notebooks in general, so I can only give you my opinion and thoughts on the issue.
Firstly, I am not very fond of the idea of using "desktop" CPUs in notebooks, to me this just negates the whole point of a notebook, thus to begin with, I would be more interested in the R40. The Pentium M, even at 1.3GHz is a very powerful CPU, but it simply cannot compare to a Pentium 4 2.8GHz, to do this you would need a Pentium M 1.7GHz. So it is immediately at a disadvantage which is not helped by the fact that the "Performance" R40 is more expensive. But the fact that it uses a dedicated 32MB Mobility Radeon 7500 (M7) is a very strong point which, in my opinion, overides everything else.
Both systems will run everything you wish to run perfectly, except the games. The G40 will struggle to run games at any resolution, whereas the R40 would run them with ease even at higher resolutions.
From my point of view, the systems are quite similar except for the processor, and the price tag ($100 difference). I would go for the R40 and fork out the extra cash, even though it is "slower". But these are only IBM notebooks, have you considered looking at Dell, Compaq or Toshiba notebooks? Dell notebooks are particularly easy to configure and price, and I would recommend you take a look at the Latitude D600 or Inspiron 600m, otherwise the Inspiron 5100/5150 would be worth a look.
I'm sure I have opened up many more possibilities for you to explore, but I hope I have simplified the process a little. If you have any further queries, please do not hesitate to contact the forums, I'm sure someone can help you out.
RaPTuRe
Who's General Failure and why's he reading my disk?