As stated, most graffiti does not constitute art because it fails to pass muster in terms of creative effort, imagination, and emotional aspect.

Your requirements are too subjective. With that logic lots of art won't be art in your standards. Creative effort? Isn't that the point of spray painting? The cognitive process that gives effort from creativity is present. Imagination? How can you even spray paint if you can't conceptualize what it looks like? Emotional effort? All things are technically done with emotional effort unless done by machince. Regardless of the emotion felt or currently present. I don't agree with your systematics here.

All of these are needed

All of them already happen. You need to find a relative objective definition. My definition is more objective than yours.

A creative, imaginative effort that fails to have any emotional impact is not art.

I disagree. Either it doesn't appeal to you or the person has done a poor job. It still counts as art. It just sucks.

Something with an emotional impact that lacks creativity is also not art. 

That is too subjective. What would we define as creative? Somethings may be creative to only a small group of people and thus qualifies are creative. All art is creative. All work is creative since it requires a cognitive process. A red dot on a black piece of paper can be seen as creative since ot can be perceived in many ways. Your definition is too subjective.

Much graffiti falls under one of these categories.

Graffiti falls under it all. A poor painting even falls under it all. You cannot objectify what is set towards the subjective.

Your assertion of placement as an aspect of those instances of graffiti that can be considered art is the first valid point you've made in that, but I still feel that that is insufficient to classify graffiti itself as an art form. We may simply just have to disagree on that.

My assertion is objective. It stands by what is realistic and measurable to all. Illegal paintings on someone else's property.

No, I don't have to admit to being in the wrong here. Your use of the term 'genre' is actually quite fitting here; music, literature, and paintings are forms of art. Rock, country, and ska are genres within the musical art form. Fantasy, Science Fiction, and Horror are genres within the literature art form. Impressionism and Surrealism are forms of painting that could be called genres, though they aren't generally referred to as such. Within music, the medium varies based on the instruments used, among other things. In literature, the medium can range from something being handwritten on paper, to being presented electronically. Within painting, the medium can be a canvass, a piece of paper, the hull of a ship, or the wall of a building.

Now you are just supporting my argument.

From that, it follows that graffiti could be considered a medium for either calligraphy or painting

You still don't get it do you? Graffiti is to art as electro is to music. It is it's own form of art. An illegal painting on someone else's property is art in the form of graffiti. An image on a canvas consisting of paint of other materials is art in the form of a painting.

but it simply doesn't fit as it's own art form;

I have already explained why it is.

I've been pretty clear, in my opinion, of where I stand- that graffiti can be art, but that graffiti itself does not constitute an art form. I'm not sure where you're getting the idea that I'm specifically biased against graffiti, nor can I work out where you're getting the idea that the subjective quality of a work determines whether it is classified as art or not.

Not really. I have explained above.

There really is not point in debating fecal art with me, even if I were to personally give it merit, it's not something I find to be a tasteful subject for discussion. Also, I am correct about the fecal art deal, and you are the one who is oncorrect!

No. Just no.