There are trolls on the site who will simply rate a game badly for no reason, or simply because they didn't like it as much they drop the rating by several points. These people annoy me no end and roughly every 6 months I forget how the rating system works and bring it up as an issue before I am lovingly reminded by 3J that the system ignores outliers and so a fair average rating comes forth in the end ignoring the trolls.
For me this means my games perpetually fall slightly short of a 7 and will most likely forever be a 6, and this is a pretty fair rating, I know several things I want to change and one is still only half finished. It also means that for the games that end up rated a 2 or 3, MOST of the readers have rated it that. A single troll or two rating it low for no reason will be ignored by the system and it will receive an average rating based on the majority of people's rating.
I do agree that the descriptions for each number are a bit silly, being made up of jokes and references that many people might not get, this has led to several threads discussing how we should rate games and what different numbers mean to each of us in an attempt to standardize some of the varying ratings.
An example of this is that for me a rating of 8 will only be given to 3 maybe 4 stories on the site, and I'd be willing to pay money for them as they are just that dam good. 7 for me means it is amongst the top games on the site, I had to have good writing, grammar, syntax, story engagement, char development and plot to name a few requirements to give a game a 7. A 6 fall just short of this, missing maybe just 1 or two of the components needed for a 7. A 5 is an enjoyable game with several issues that need fixed (but if they are fixed I'll come back and re-rate it). A 4 is a good try with the basics of a story in place but one that needs a lot of work in several areas,usually these are in the plot, grammar and char development areas. A 3 for me is someone who clearly tried to do somthing but sadly this time failed, these are cases where I can see the author honestly tried but there are so many problems with it that is becomes much more of a chore to read it due to my eye constantly being drawn to issues rather than what there is of a game. 2 means... Well if I rate a two then it means the author didn't really try, they might have had a good idea but they clearly didn't put it the effort of even trying to expand a plot, chars or make the sentences read correctly. 1 is reserved for troll games I think need deleted immediately.
That is the system I use so I mostly ignore the descriptions given for each number apart for occasionally to laugh as I remember the joke or reference. I also know that many others have a similar system for rating games. As for the issue of very short games getting bad ratings, this is usually because they fail to meet so many standards, short games that manage to develop chariicters, plot points and storylines would get a great rating for me as I love the short story genre, the issue comes with the majority of short length story's on here. The generally are very linear with little to no plot or char development. Some that I personally rated a 2 jumped in by telling you your entire char and background in 1 paragraph before having two lines on each page to progress the story, every page being a choice between the 'right' answer and 'insta-death' then end with a 3 line description. That is why they get a low rating.