Rap and Hip Hop are NOT one and the same. There are as difficult to discern their individual usage as words in the English language that sound alike but are spelled different and have completely different meanings to someone trying to learn English as a second (or third or fourth) language. Here it is in a nutshell.
Rapping is the ACT of rapping whether it's being done badly, accapella or over a beat. If you are not an emcee then attempting to spit a freestyle or a prewritten rhyme (written by whomever) is referred to as rapping regardless of if you are a contributor or fan of Hip Hop culture/Rap music or not.
Grime emcees aren't "rapping" per se because Grime isn't Hip Hop. This means they are neither "Rappers" or emcees in the "Hip Hop" definition. There are emcees in the "Grime" definition and the aesthetics of the flow and delivery and beats are all different. They AREN'T "rapping" they are "emceeing" in the Grime sense. Confused?
"Hip Hop" involves actually being a fan of/lover of/contributor to the worldwide culture of Hip Hop. If I was to spit a rhyme I'd be "rapping" and "emceeing" in the Hip Hop definition. If Lindsay Lohan spit a rhyme in one of her songs then she's just rapping because she sure as hell ain't an emcee or a Hip Hopper.
Does that work for everyone?
One.
No it doesn't work at all. You can't say that quality decides what rapping or MCing is. According to what aesthetic are these judgements made? Who gets to set the criteria? This is really subjective and makes absolutely no sense. It's also not at all useful in the context of the original question.
I'm glad to see that you said exactly what I thought you would about Soulja Boy, though, because it at least means that I understand what you're trying to do. It's just wrong, as far as I can see.
Calling artists like him a "rapper" or his music "rap" as opposed tp "hip-hop" by way of an insult is actually pretty problematic. For a start, they're actually not very good rappers at all! If you think about it sensibly, neither Soulja Boy, Hurricane Chris, D4L, Mike Jones etc blah blah blah, nor Jeezy should righfully fall under that category. What you don't like about them is that they can't rap, so why use the word "rapper" as a derisory category? It doesn't add up.
Using "rap" as a lower-league subdivision of MC-based US black music and "hip-hop" as a term of canonisation and approval is far too complicated for the vast majority of people to grasp, even if the criteria of what places an artist in either category could be agreed upon somehow — which they never will . It's way too personal to work in any realistic way and, if you analyse what you're saying, you'll also have to concede that those people who do know a lot about hip-hop culture and possess a fairly nuanced understanding of it will also find plenty of fault in it.
Let's not get caught up in what is or isn't rap or hip-hop according to purist dogma or personalised value judgements. It's polarising, agenda-driven and not very helpful. Rappers are people who rap, an MC is the same damned thing, hip-hop is hip-hop, some of which some people will like, some of which others won't. Simple.
The truth is that all the people you call "rappers" do rap (regardless how well or badly), also they are absolutely hip-hop. There's no real doubt about that. They're just hip-hop that people like you happen not to like.
Also Dart. your definition of the MC contradicts itself, and quite seriously, too. How can the term MC be used for all that which is good and wholesome and real in US hip-hop and then be used to mean anyone who picks up a mic in grime, baile funk, most reggaeton etc? How can "rap" be used as a perjorative as regards "real hip-hop", but be a protected, almost nationalistic term that can never apply to non-US oral music traditions.
This is confusing and doesn't make sense. Better just to say that rapping and MCing are pretty much interchangeable terms in most cases and that there are differing schools of thought as to the validity of individual artists who rap/MC, otherwise you get yourself and everyone else into a huge, obfuscatory mess.
***** A side issue here, thanks to whoever said dancehall deejays also rap: no, they don't really. That's why I didn't include them in my list of genres. They toast. It's very different to rapping in all sorts of ways. MCing in patois = toasting.
Toasting is the term used within reggae. As far as I am concerned, it should also be used by anyone discussing dancehall or reggae deejaying. As Jamaican music inspired hip-hop and, along with all manner of other African/African American oral traditions, is right at hip-hop's roots, deejaying shouldn't be filed under "weird Jamaican rapping". It's pretty careless, but in its widest sense this can also be seen as a culturally imperialist, revisionist position, making Jamaica submissive to North American culture, denying reggae's/Jamaica's influence on hip-hop/North America.
Reggae and hip-hop are family, but reggae's innovations came before hip-hop (and disco and the rave continuum, for that matter). In music, where Jamaica goes first, the rest of the world usually follows. Without Jamaican music, hip-hop would not exist in anything like the same way. Bearing this in mind, it's important to recognise and refer to Jamaican music's conventions in the correct way, otherwise you run the risk of privileging hip-hop over musical styles and paradigm shifts in form that have existed for longer and been exteremely influential on hip-hop's own development.
***** This also throws up the question of what grime mcs do. I wasn't thorough enough in my explanation. Grime MCing in most instances can be described as rapping, but not always. Grime's oral culture (also its sonics, but that's not so relevant here) is fundamentally a mish mash of British rave MCing, dancehall and hip-hop, therefore it crosses the boundaries of toasting and rapping in a way that nothing else really does. For example *most* grime MCs rap (e.g. Durrty Goodz) others toast (e.g. Flowdan most of the time), some do a bit of both (e.g. Riko) . In this instance MC is a better term than rapper, because it encompasses more. My preference for this term is not about genre ownership or anything else, though, which I think Dart's is, it's purely functional.