There's no such thing as too long for a good storygame. It's pretty hard to make a good one though with under ~4k words (normally). Writing also takes a bit longer due to organizing a branching story together. That's not even considering the use of scripting.
Storygames are really deceptive to write. Let's say you have a plot that should take 5k words to finsih. It'd normally be a short story, but as a storygame you decide to have three branches. Now, the "short" story has turned into 15k words (5kx3). A small work can easily multiply into something gargantuan before it is even written. Oh, let's say there's wrong choices in you story as well leading to a quick ending along the 3 5k paths. It could add 2k each which puts your story to 21k words.
This is also why you'll see very few more traditional storygames. Some examples of this approximate style includes basically anything by End Master and Dead Man Walking. End Master's Eternal and Dead Man Walking also happen to be the two highest rated games of the site and at 632k and 1,083k words respectively.
Nonetheless, there are other styles! Hurray! We have a whole bunch of them. You'll see them all after reading enough storygames, but this article has it all and does a really good job explaining them.
So, what does all of this mean for me? You basically just did an info dump.
Good question. One of the most common thing you'll see on storygames' comments beyond the generic is "It was too linear" or "I liked the choices". No matter what style you have, don't make it blatantly linear. Generally, anything beyond two pages with just a single link starts edging into a "this section was linear" category. You'll need something. It could be a brand new branch, a wrong "bad end" choice, or simply one that applies an illusion of choice. (The illusion of choice is basically having two links to two different pages that link to the same page instead of truly branching.)
Cool, um, what should I shoot for with my word count?
With new members, we generally tell them to start small. Get used to this different form of writing before tackling it. One member (who has been around for years but never published anything) recently did this. It's a good example of a first storygame. It has its flaws which are noted in the comments. Most notably is probably its length at 2,637 words, but it still received 4.83 rating. Also, you'll receive more grace on your first storygame. People will give you advice and such, but we also hope you'll try to improve.
If you want to test out sections from your work before it's published, we have the Writing Workshop for that reason. If you want it all tested, ask for a beta-reader (who you'd send the storygame's link to and he/she would read it and give you their thoughts).
I didn't intend to be so long, but I suppose I became carried away. :)
For comparison, the King James Bible has 783k words.
I'm glad you posted the link to the styles article; I'd never seen it before and it's an interesting read.
(Also, at least you were thorough in your getting carried away-ness.)
It's also important to recognize that different styles and genres of stories work better with different styles of game. I can't speak for anyone but myself, but I find that when I'm reading a puzzle game, I don't want a lot of 'empty' description and I prefer shorter pages. When I'm playing a game that is entirely (or almost entirely) story, then I want much longer pages and more filled in details.
Also, you have to determine which way of doing paths works best for you. My first game here I tried to finish up all the 'side' and 'short' endings first. By the time I was done those, I had run out of time for the contest I was in and only ended up with 2 major endings when I had initially planned for 4-6. This time through, I'm trying to write a single 'main' path to its conclusion and then I'll go back and flesh out the rest. Without being in a contest, this might not be important, since you can bounce around all you like, but if you're the kind of person who needs to focus on one thing at a time, then it's good to know that about yourself.
I tend to be the same way. Which is probably why I rarely finish anything.
Some advice I'd give you:
Don't do short 3k stories and say they're part of a "series" as those rarely go anywhere.
Include a nice amount of options as appropriate for the story. Try to avoid false choices (such as options that force you to eventually select one of the options to propel the story, and don't kill the character every other choice).
Take your time, add nice but not over the top descriptions. Sprinkle in a good amount of character development and personality.
Most of all, just keep writing. It may take a while to publish a good quality story but it will certainly stand out from all the crap smears the lesser writers have left behind.
"Don't do short 3k stories and say they're part of a "series" as those rarely go anywhere."
The rest of the advice is also good, but nobody likes a small teaser of something bigger/better that never comes along.
"If you write one story, it may be bad; if you write a hundred, you have the odds in your favor."
Edgar Rice Burroughs
If this guy saw the "series" on this site, he would recant this statement.
Has anyone actually completed a hundred stories on here to get those odds? ;)