OK theres a lot of bits of info here, let me clarify this.
First of all, PLEASE buy some books, search google, etc. There is a lot of this basic information out there already.
Second, Aspect Ratio is only part of what Super 16 is.
16 mm film traditionally has two sprocket holes on either side (this is called double-perf), and a 16mm camera will let light onto the center of the film 24 frames per second, or whatever you prefer. The actual size of the recorded image is 10.26 by 7.49mm = 76.85 sq. mm and that produces a 4:3 or 1.33:1 Aspect ratio. This is great for 4:3 TV's but not so great today for cinema because most people now have widescreen TV's and in cinemas they are all widescreen, not Academy (1.33:1) like the old days. You COULD get around this by letterboxing in post, but you would essentially be throwing away resolution of your picture.
Where Super 16mm is superior is that it has a recorded image of 12.52 by 7.41 mm = 92.77 sq. mm, and this is 1.66:1 Aspect Ratio, which means that natively it needs no or very little letterboxing to fit HDTV, and fits fine to be projected in cinemas. Super 16 works by removing the sprocket holes on one side of the film, and recording picture out to there. So if you were keeping track, Super 16 is 20% more negative recording area than 16mm, and thats just to start. If you were to crop/letterbox the 16mm in post to achieve a widescreen, 1.66:1 or 1.75:1 AR, you would lose about another 20% of recorded negative,
therefore, by recording s16 vs. 16mm and ending up with a 1.66 or 1.75 AR, you would gain roughly 40% recorded negative, and as we all know, recorded image area = resolution.
The issues of s16 is basically it cannot be projected natively (there are really no known cinema projectors for s16), but thats not really a problem because I doubt you'd want to project the 16mm image from a film print anyway. Also, the wider image means you need to use super 16 lenses, and you must use single perf film. None of those are limiting anymore because single perf film costs exactly the same as double perf and s16 lenses, or more properly, 16mm lenses that will cover the super 16 gate are abundant.
Remember super 16 cannot be shot with a regular 16 camera without modification. At a minimum, the lens must be recentered, and the gate widened. If the spindles inside the camera only have one sprocket, thats fine, otherwise if they have two, that will need to be modified as well.
Finally, s16 has one other major advantage. It is the closest thing you can get to the aesthetic as 35mm. It uses the same stocks, and in the right hands can produce a semi-shallow DOF, which combined with good lighting can produce an image that looks very close to 35mm. Also, it can be blown up to 35mm relatively cheaply in a process in post, FAR cheaper than going from digital to film. So in other words, s16 offers many great advantages in this day and age for a motion picture.
1) It offers a similar look as 35mm.
2) It can be blown up to 35mm with a simple inexpensive process.
3) It can be scanned and shown in high definition with relative ease (the AR is pretty much the same and there is enough resolution there to hold up).
4) The cost of shooting s16 vs 35mm is about 1:3, and it is right about the same as shooting high definition (on a pro camera).
The downsides:
1) Requires s16 camera and lenses.
2) Requires single-perf film.
3) Cannot be projected natively (you would need to transfer to something else to project.. but then again you can't really project negatives anyway).
4) Is not point-and-shoot like digital is.