Besides the obvious limitations of having cartoon style split only to non-specific cartoon styles and anime/manga style cartoons, I'd like to expand that a bit. Not too much, but so people can have some sort of guideline to distinguish them.
There's some obvious styles already tagged, such as: caricature, chibi / suber deformed, and some made up concepts for fairly consistent features.
There's also few tags that are very ambiguous but cover some corner cases, such as stylized.
Things that are missing (in realistic to non-realistic order):
* Semi-realistic cartoons - as seen in many serious western comics. Cartoonyness is extremely limited, such as heavy outlining, flat shading, but otherwise style is fairly realistic.
* Cartoony or heavily stylized. - Zeno Clash, Smite, Warcraft 3, Starcraft 2, Supreme Commander 2, League of Legends, Dota [2], etc. games with somewhat cartoony style but try to stick to realism in how they function.
* Noodle people and other things that have lost any realistic sense of anatomy (underlying muscles and bones) - Sonic the Hedgehog series, Hello Kitty, New Zealand Story, Mario Bros, etc.
* Completely imaginary shapes and forms where even humans sometimes look like bizarre creatures - Real Monsters, Psychonauts, Rayman series, etc.
Those essentially cover 2 realism heavy cartoon styles and 2 cartoon heavy cartoon styles (sounds redundant, yes).
Besides visual style, cartoon physics/realism or lack of it in games marked as cartoon should be noted as well since it covers a method of breaking realism besides visual style.
Cartoon characters can be depicted regardless of style too though, so presence of cartoon characters in non-cartoon or semi-realistic cartoon games would be notable. Though this could be generalized as style mixing.
Cartoon and not so cartoon
Complicated issue. I also often wonder whether to mark something as cartoon or not. Reading the wikipedia article about what a "cartoon" really is I am even more confused. Comics like Batman or even more realistic graphical novels are something that I personally don't consíder as being "cartoony". Same for many animatied series with more or less realistically drawn characters. Bugs Bunny, Pinky & Brain, Donald Duck... those are Cartoon-Characters for me. In a broader sense I accept series like Flintstones, Jetsons etc. as Cartoon. A series like Simsons is already a border-line for me. The rest I just leave out because I'm not sure.
Well, there's photorealism, which doesn't exist in games yet AFAIK. So we obviously need to leave a rather broad semi-realistic territory out of cartoon style already. The 4 categories are however for things that have certain traits that definitely identify them as cartoons of varying extend.
A lot of anime comes close to 'semi-realistic cartoons'.
There's rotoscoping cartoons (like Lord of the Rings) where real images were converted to cartoons and meant to convey a realistic depiction. A more recent example would be A Scanner Darkly. I'm sure I saw this in a cut scene for a game somewhere, but I can't recall. This is different from Dragonslair, where the same process is meant to convey a cartoonish depiction.
There's rotoscoping cartoons (like Lord of the Rings) where real images were converted to cartoons and meant to convey a realistic depiction. A more recent example would be A Scanner Darkly. I'm sure I saw this in a cut scene for a game somewhere, but I can't recall. This is different from Dragonslair, where the same process is meant to convey a cartoonish depiction.
Speaking of rotoscoping, the tag itself covers some games that could be considered semi-realistic cartoon style (Prince of Persia especially). They're all however in the border territory because of limitations of hardware back then, but I would purely on that either dump them into realistic non-cartoon or the semi-realistic cartoon group, in the latter for sake of principle, in the former for sake of "platform limitations".
Need some descriptive words for these broad styles. The first one can easily exist as `semi-realistic´. Stylized is probably good for the second one, since the last 2 can't really be any more called stylized regardless of the specific style and semi-realistic shouldn't be describable by it either (as in, it should omit anything that could be described as such). The two last ones can be said to refer to styles from the golden age of cartoons (Wikipedia and TVTropes) so they could be dumped together in that somehow, though I personally would like to distinguish them.