Great Tutorial.
Unfortunately, a lot of people seem to think that reproducing a game is equivalent to stealing it. To get a higher score you might:
1. Use snakes or other animals instead of fishes, so trigger-happy blammers will not immediately cry, "STOLEN!" Also, make a credits section in which you mention X-Gen studios and Fishy. I'm willing to bet that the people who voted low on this are the same people who would not check a credits section.
2. You say that you don't give the entire game prepared for the purpose of learning, and later state that you will not comment on the code because of lack of time. Seems kind of contradictory -- just get rid of one of them, or comment on the code a bit.
3. For people who know nothing of Flash, just give a .fla with the entire game prepared. Even if it involves sinking to a new moral low, it will raise the score.
4. I don't have a working set of headphones/speakers, but in the reviews it seemed sound was a problem. I can hardly be critical of that because I don't know, but adding/modifying the sound might raise the score. Also, if there is no sound when you eat a fish, you could add that.
5. Improve on the graphics slightly. Some people will just play the game without reading the tutorial. If you make the fish explode/get bloodied, people who vote solely on graphics will vote higher.
6. Say important information in caps. Obviously, people cannot be bothered to read a couple of words to understand how to change the speed.
7. At least comment a bit on the code -- it needn't take months, just simplify what the most basic/important parts of the code mean.
8. A lot of people criticize the background of a tutorial. I can't personally see why you would need anything else except a white background for a tutorial, but you couldn't go wrong if you took a low-alpha snapshot of the game and used it as a background.
Anyway, this was one of the best tutorials I've seen up to now. I'd give it a 4/5, but I'll give it a 5/5 because it had such a low score.