I'm certainly not the best person person to answer this, but I'll add my thoughts. 

When you're talking about rating baseball cards or a lot of collectibles, you'll have a specific rating system by a group of professionals (CGC, PSA, GIA, etc.). What they're comparing to is an idealized form. They know exactly how that card or comic book should look brand new. Which shade of coloring, alignment, if there's any known misprints, what denotes a first run, and a slew of other details. There is a standard for every metric of that item. Because they're mass produced to some degree, and that is publicly available knowledge. 

With knifemaking...that becomes a bit more difficult. Because when it comes to ABS rated knives, they're not mass produced. There certainly are collectors of mass produced knives (case and buck knives especially in my experience), and then you get your military or historical knife collectors who are their own special breed of dedicated, but for ABS you have to approach it more like looking at art. Which means there's wiggle room for interpretation. There is no agreed on idealized form, even if there are key elements that the ABS sets for a good presentation knife. But if you look through the judging guidelines with a cynical eye, you'll see that they give testers a fair amount of room to experiment with. Even with the MS Quillon Dagger. They try to give just enough guidelines to make sure you demonstrate the different skillsets they're looking for, without setting a strict standard of what will or won't pass. If they did that, it would read more like engineering blueprints and we'd all be presenting the same uncreative blades. 

It's also important to note that by giving out a rating certificate, that would be like the ABS saying "this knife would pass the presentation portion". Which they won't do. They also make it clear that just because one Mastersmith says a knife looks good doesn't mean it will pass, and they heavily encourage getting knives looked at from multiple Mastersmiths if possible before presenting. But the only time they decide if a knife actually passes or fails is on that presentation day. 

Another thing I think about is certain knife elements the ABS doesn't like (at least for presentation knives). Take something like serrations. A spanish notch here and there maybe? But not serrations, and a lot of good knives have serrations for good reasons. Or something like a single bevel knife. There are a lot of fantastic single bevel knives out there, especially in the japanese culinary world, but because it throws symmetry off it's not what the ABS is generally looking for. So already you can see where what the ABS sets as a good knife for presenting isn't the end-all-be-all of good knives. It's just what this organization looks at. Clean, balanced, and symmetrically forged knives. Even something like a brute de forge knife, no matter how well made and beloved in the community, isn't what they're looking for in a presentation set. Even if a lot of customers in the outside world absolutely love it. Hopefully that can explain some of the discrepancies you're seeing between what's normally presented for sale vs what's a good ABS presentation knife.

So how do you know if it's an ABS presentation worthy knife? You looks for that JS or MS stamp/marking, compare that maker against the ranked member list provided on the ABS site to make sure it's not someone just saying they are, and then you can compare that against the guidelines for presentation to see if it's in the realm for presentation level or if it's a great knife but not necessarily the type of knife for judging. The ABS also provides some photo examples of passing sets on the website, and a lot of makers get their passing sets professionally photographed and you can see those under the 'links' portion of the website where they have several knife photography links. Those help you develop more a feel for what you're looking for. But also don't be afraid to ask at shows if they have knives by ABS smiths so you can get your hands on them and solidify that feeling. Even if they don't, at least then you know the answer. And it's always surprising to me how many people know-a-guy-who-knows-a-guy and they can get you what you're looking for. 

What about other knives and grading them though? There used to be the NKCA for knife collecting, but I believe they're defunct or very nearly so. Then you had the National Knife Museum, but they dissolved. So now you have certain specialized collector groups, some of which have a more strict governing body for grading (look at the NBTHK for japanese stuff and see how strict some of their stuff is) and some are just collectors. So if you have a particular type you're interested in, searching for it with the word 'collector' can often lead you down the right rabbit holes and forums. 

It's also good to remember that saying I have heard many an MS repeat.
"Once you get the stamp, you can make whatever you like". The test is just a point in time for a maker.
This is certainly true of some rated smiths who once they get that stamp, rarely make another knife that would pass the test again. Are they still making "good" knives? Probably so. Some things you never loose. Hopefully, they are the important parts of making a knife.

So if you are out looking at knives in the world, at shows, stores, online, or whatever, to get some idea of what will pass, you are looking in the wrong places. You should be looking at images specific to the test, i.e. sets of knives that have passed. You should be reaching out to rated smiths and talking to them about their knives and their processes, asking them to evaluate your work with respect to the testing. 

Caveat: It's really difficult to give a full critique from a photo and it's also difficult to look at a photo and "see" those details the tests require of you as a prospective JS or MS.

Now as to the rating system, there isn't one because as Bobby pointed out, there isn't a universal standard. The ABS has a standard for testing, as do other knifemaking organizations. There are many groups of collectors who look for specific characteristics or styles, but this is as varied as types of apples. It's easy to confuse the standards for testing with the standards for "good". "Good" is subjective. Everyone has a different opinion of what that is.

I always chuckle to myself when anyone says "The ABS style of knife." What does that mean anyway? I've been around ABS smiths and non-ABS smiths for a long time and I can tell you straight, there is no "ABS style". The closest I have ever heard of an ABS standard of a "good knife" is one that looks so good you want to pick it up and feels so good in the hand you want to cut something with it. 

Thanks folks, I just figured I would ask.