So, it depends on what you're trying to replicate, here. The G16 is a small-sensor camera, but a fairly nice one, and you can get good results in good conditions, especially at "web sizes" as shown on photo-sharing sites.
One thing I want to note to start is that the perfectly straight vertical lines strongly suggest that this photo was shot in RAW and had perspective correction applied (an easy thing to do in, e.g. Darktable (see video tutorial)). (In fact, the image tags include "Lightroom", which doesn't prove that the correction module was used, but is strong confirming evidence.)
If you look at a Flickr search for "skyline" photos taken with the G16, you can see some pretty nice examples, including similar night shots; the difference between the average example there and your example isn't the camera — it's the care taken in setting up the shot and some quick work in post-production.
So, on to camera settings. In terms of exposure, the sensor size does not matter. This is because sensor size is just like cropping out the middle of an image, and, obviously, if you take a photo and cut it in half, it doesn't suddenly get darker or brighter. So, from that point of view, the way to replicate f/5.6, 15 seconds, ISO 160 is — f/5.6, 15 seconds, ISO 160.
But the sensor size does have some effect.
When you're comparing depth of field, the ratio between the sensor sizes can be used to get a rough equivalency. That is, the SL1's 26.8mm sensor diagonal divided by the G16's 9.4 gives a ratio of about 2.8:1, so, you will find that you get the same depth of field on your G12 at f/2 as the SL1 gives at f/5.6. If matching DoF was your primary concern, you could take that three stop difference in aperture and decrease the shutter speed by three stops (that is, 2³, or 8× — see shutter speed stops formula/math) to about 1.9 seconds.
But, before you do that: this is really only important if you're trying to match background blur. For landscape/cityscape/skyline photos, generally what you want is more depth of field, so I'd guess it doesn't matter if you actually use a smaller aperture equivalent — it's in your favor, in fact. So, I'd experiment with the sweet spot for your lens — possibly you get the best results wide open, or just stopped down a bit. (But, actually, wait and see below on shutter speed!)
Second, the issue of ISO. There isn't an equivalency here really, but let's go back to the cut-in-half picture. The exposure doesn't change, but it is true (hopefully obviously) that each half has half the total light. As a rule of thumb, that roughly means that every doubling in sensor size gives a noise advantage of halving ISO. The SL1's APS-C sized sensor is about 8× larger by area than the G16's, which means when you get to pixel-peeping, the SL1's noise performance at ISO 8000 might be about what you get at ISO 1000. But, on the other hand, sensor technology is amazing these days. Make sure you're not under exposing, and especially when not analyzing with a magnifying glass, and results will be fine. Generally, you should strive to keep this as low as you can, while getting in enough light.
Finally, the shutter speed. In terms of effect on the photo, this might be the most important, and also, the one that doesn't change with sensor size. Note the smoothness of the water — a longer exposure will make that even more silky, and a shorter exposure will make individual ripples and waves more apparent. So if you want to match the original, you have to keep the shutter speed the same.
Putting it all together
Presumably the light in your scene won't be exactly the same as the above. So, you'll need to watch your camera's meter, histogram, and possibly take some test shots. Once you work that out, though:
- Set the shutter to 15 seconds. Use a tripod, because even with image stabilization you can't hand-hold for that long and get a very sharp result.
- Let the aperture and ISO fall wherever they want to to match the exposure, possibly experimenting with keeping them constrained to values most optimal for your camera.
- Shoot in RAW and apply distortion correction after.