From what I gather the lower the aperture number, the brighter it is, which is a good thing, right?!
It's a good thing if you need it.
But does the range matter?
Yes and no. The range isn't largest capable aperture to smallest capable aperture; it's largest capable aperture at the shortest/widest focal length ("zoomed out") to the largest capable aperture at the longest focal length (zoomed in).
To build on your example, both the LX5 and S95 can do f4.9 at 90mm, but only the LX5 can do f3.3 at that focal length.
is F2.0 an absolute must or is F2.8 sufficient?
Again, it depends on whether or not you need f2.0 In other words, how often do you shoot in conditions that require a larger aperture than f2.8?
Is 1/4000 an absolute must or will the 1/1600 of the S95 suffice?
Similar answer here. How often do you shoot in conditions that require shutter speeds faster than 1/1600?
So between largest shutter range, largest aperture range, lowest aperture number and lowest shutter number, which are the most important things to look for? For instance, would you go for a G12 with a faster shutter time or a S95 with a brighter lens? Or go for the LX5 which has the best of both, but a smaller aperture range but a larger shutter range?
Again, what are you shooting? Are you trying to freeze the wings of a hummingbird in flight? Or are you trying to take a picture of a kid blowing out candles on a birthday cake?