I have several stories I feel I can tell through a myriad of mediums - but what I am interested is actually getting them published. Since none of you have seen my writing outside of forum posts and maybe a snazzy avatar, please just assume publishable quality. This isn't a question of my current skill. This is a question of the long run. Could any one attest to the odds of getting a story published as a: novel v. graphic novel v. TV script v. film script?
I'm not sure about how likely your stories are to be picked up by a TV/Movie company but if you go down the graphic novel or novel road you could self publishe it. I'm not saying it would be cheap but you could always use Kickstarter or IndieGoGo to try and raise the money.
If you self publish there's a certainty that your work will be published, in any medium... You've given four examples which all require different skills (even TV and film are quite different), so to have the best chance of becoming published you need to pick the one that you are best at. For instance, whether or not a graphic novel is easier to get published, I can't draw so that means for me there is no chance of using that route. Also, how can your ideas best be expressed? Some things work best as films, some as novels and others as graphic novels. All routes could lead to publishing, but I reckon it's your own skills and the ideas that really affect the likelihood.
From what I've read, getting a screenplay sold is even harder than getting a book published. I have no idea what the odds are as far as graphic novel over regular novel.
Ditto CH878 Find the perfect medium for your story - sure you can tell any story in multiple medium but that doesn't mean every one would fit. For example the film The Artist - it won many Oscars and it is a silent movie, with clever uses of sound and speech. Having seen it, and loved it, I can say that the silent movie mode was absolutely PERFECT for what the film was trying to express. It would not have been half as good had it been a normal movie - it had to be silent. And for this reason, it won me over all the more.
To expand on what CH878 and Mckk said, there are two things to consider - your particular storytelling strength and the nature of the story to be told. Some stories are best told through dialogue, and the interest is built up through the personal interaction of the characters, with little or no chance for narrative. To see those stories in the format of a novel would be tedious for the reader, with page after page of dialogue, and difficult for the writer, with the constant need to add SOME narrative with which to balance all the chatter. Some stories are incomplete unless descriptions are given of place, of time, of thought processes. They need narrative, and character interaction relies on other descriptions besides dialogue. Such stories do not translate well into plays or films. At the same time, you don't have to scan these forums very much to see that there are some writers who struggle with the dynamics of dialogue, while others struggle with the right way to cast a narrative (and often fall into hard-and-fast rules to keep them on the track). What kind of story do YOU like to tell, and how do you like to tell it? In any writing project I ever take on, I always have some sense of what I want it to look like before I start - an incomplete sense, to be sure, but a sense nonetheless. Sometimes I can see just what the ending looks like, other times I can see a particular scene or interaction at a particular point in the story. I have written one play (first draft, anyway), and the reason I wrote it as a play was because I was best able to visualize several of the characters on stage. I understand your desire to be published. But in the final analysis, the odds of being published (other than self-publishing) are all about the same - slim to none. What will ultimately determine if you get published is producing a quality work. Picking the best medium for your story and making sure you are comfortable with it will go a long way to making sure that happens. Best of luck.
to answer your question, the chances of succeeding in any of those mediums are about the same, for a new and unknown writer... slim to none... with writing for tv being somewhat less than the others, since if you're not already working in the industry and don't have solid connections there, no one will even look at anything you want to submit, thanks to the dictates of their legal departments...