Let me break down how the restaurant rating system works on the site, since it's a bit different to the norm.
The idea behind this system is that a system based on scores/grades/stars isn't usually suitable for every day use. For example, a restaurant may be rated 15/20 but because it's fairly expensive or it's too formal, you may frequent a restaurant rated 10/20 more often.
Most rating systems will favour fine-dining restaurants like Tetsuya's or Quay, simply because they're supposed to have good food, service and atmosphere for the price. Surely an awesome tapas place--one that has above average tapas and an excellent atmosphere for a good price--should also rate highly? Sure, the service might not be as polished as at Tetsuya's, but what if it's great when you compare it to similar restaurants?
So our system rates the restaurant according to how well it competes with similar types of restaurants, how well it reaches what it's set out to achieve and how exciting it is to eat there. Take, for example, the review on this blog of now-defunct Omega. While the food was exceptional and it ticked a lot of other boxes, it was lacking in some areas when we visited. So the next time we were looking for a dinner of that style and that price-range, we looked elsewhere.
Compare that to the review of Chinatown staple, Chinese Noodle Restaurant. Right there is a place that makes you want to go back to over and over because, for the money you pay and the food you get, it's superior to similar places (at least in our minds).
Let me break down the different ratings:
Will constantly return to - For something to make you want to constantly return to it then it really needs to be doing something special. There must be a very clear distinction that this place is above it's peers. You will fight for this place and recommend it to everyone who will listen.
An expensive fine-dining place can still receive this rating but it doesn't mean that we have the cash to go there once a week. It means that when we have the appetite and budget for some fine-dining then this place will always be considered.
Will return to - Still a very strong rating. A restaurant at this grade will be consistently good. You will want to go back there, but it doesn't quite have that same level of excitement as much as a place in the higher category. You'll still come here every now and then (and enjoy it!) but it's in competition with many other enjoyable places and new places that you're keen to try.
Okay, may go back - While this is still a good restaurant, it does have flaws. You wouldn't go out of your way for this restaurant, you'll rarely consider it as a dining option and probably wouldn't recommend it to people. If you're nearby or if someone else suggests going there, you won't mind too much, but you won't be too excited by the prospect.
Will probably not return to - This is where it gets unfavourable. The flaws are at a point where you wouldn't go here, even if you were in the area. You would only go here if someone else suggested it and they weren't interested in your alternative suggestions. You probably only go here out of duty to someone.
Will never return to - They have either stuffed up massively or just aren't offering anything good to get this rating. To get this rating, it needs to be so bad that you just do not want to go back under any circumstances. Even if someone suggests this place or organises a meal there, you will resist as much as possible.