Here's what the game ratings on this site approximately mean:
total crap, not worth to be in existence
has something to it, like professional production values, a somewhat nice idea behind it, but is in the end not seriously playable
not that bad; certainly has some redeeming value, but also very serious flaws which, at least at some point in the game, make frustration or boredom overwhelming
good game, definitely worth playing for longer than half an hour, but absolutely nothing special to it - a game made 'by the book'
very good game, almost all important aspects come together in a good way; a safe recommendation
excellent game, a 'must-have'
pure genious, the best of its kind
Before you get mad at the person who gave out a bad rating to one of your favourite games (or the other way round), please keep in mind that there is no such thing as an objective rating. Although we try to keep it as consistent as possible, these little numbers should only act as a very rough guideline.

You also have to be aware that 0-6 scale we're using doesn't leave room for many nuances. For many games, two different ratings could easily be justified, but the reviewer always has to decide which one to give. Here are a few examples of how we come up with a rating (compiled by Mr Creosote, so the ratings and reasons are his):

Curse of Enchantia is a total failure gameplay-wise, but it's also obvious just from the looks that some professionals were at work there. Rating: 1.

Winzer is so dry and boring that it's almost funny again. It could even have some appeal to die-hard fans of business games, so the rating could as well be one point higher if I had been in a better mood when reviewing the game. Rating: 1

Der Rasende Reporter is a very obvious one: Lots of good will can be found in that game, but in the end, it's way too primitive. Giving that game an average rating of '3' simply wouldn't be fair. Rating: 2

Fist 2: The Legend Continues is almost uncategorizable. The main part of the game is dull, but the included 'bonus game' is almost an exact copy of the game's (superior) predecessor. Which part should be rated in such a case? Or would it be more logical to 'rate' both and settle for the numerical average? I went for basing the complete rating on the new part of the game - very debatable, of course. Rating: 2

Operation Stealth is an average Adventure - until you play long enough and get to the action parts. A classic case of the definition of 2 given above.

Chaos Engine 2 is a tough case. Compared to the brilliant first part, it's a huge disappointment, so it's tempting to give out a low rating. Seen for itself, it can at least stand up to standard action games, though, thus the average rating of 3.

221b Baker Street falls exactly into the middle of the rating scale. It's just the board game, nothing more, nothing less. The board game is nice, but not more. There's nothing to set it apart from other board conversions. A classic 3.

The Spy Who Loved Me offers exactly the kind of action you'd expect from a James Bond - game. You can smell the routine which went into this production - both in a positive and negative way. Rating: 3

Spidertronic got close to the '4'. It has originality which is rare enough. If it weren't for some unfair level design, that would have got the game an additional point. Rating: 3

Blade Warrior has pretty average gameplay, indicating a '3'. Original, stylish presentation got it an additional point - 4.

Hannibal is a very accessable wargame, putting it above most of its competitors. The very good first impression can't be justified later on, though, because there isn't enough interesting stuff to keep non-genre fans glued. Rating: 4.

Noctropolis manages to score highly in almost all areas of Adventure gaming: story, puzzles and graphics. It spoiled its own rating by the addition of hideous videos with horrible acting - 'only' a 4.

Ambush at Sorinor adds a very original twist to its excellent predecessor Siege with its mission system. Rating: 5.

Bureaucracy is one huge insanely funny trip. Just think about the bank puzzle - 5.

The Settlers is a modern classic. Hardly anything could be done better. At the upper end of 5. Why it didn't score '6'? No idea, that would be justifyable as well.

The Secret of Monkey Island is one of the few games with a perfect rating of 6. It's probably the most popular game ever, and deservedly so. Usually, the line between a 'good 5' and '6' is thin and extremely subjective. In this case, it isn't.

Hopefully, this made things a little clearer.