I voted a 4-5 but, after doing some real thinking about it, I would up that slightly to a 6. Here is my reasoning, from good to bad:
Graphics: 10/10. This is where they have really excelled and have made a truly stunning and beautiful looking game. Sometimes you are just blown away by the look of something (the overhead "helicopter" view of the sweeping turn 2 at Willow on a replay is my most obvious example....I watched my Ford GT through there and was blown away by it);
Cars: 10/10. The sheer range of cars is staggering and, while some cars are pretty pointless (Kubelwagen and too many to count MX-5s to name a couple), to see some of the most iconic cars in history and drive them is immense. Yes, standards are disappointing, interior-wise, but I can accept that;
Tracks: 10/10. The number of tracks is impressive and, to be able to drive on some iconic tracks is great fun. They have chosen excellently when considering new tracks to bring: Brands Hatch, Silverstone, Batthurst, Willow Springs, Ascari....each has it's own charm and character and adds such a lot to the already good line-up;
Interface: 8/10. The UI is good and, while I prefer the GT5 interface (Sorry, but I just do.....I prefer GT4's over both though), I do like the cleanness of it. It is easy to find what you want;
Content: 4/10. While the game has excelled with the number of cars and tracks, it falls short in terms of the content. GT5 was rich with so much variety, be it enduros, B-Spec, all the Special Events, Seasonal races etc and GT6 is a distant second in this respect. However, I can only compare to GT5's finished product as I bought it late in the cycle. The game doesn't have enough offline content to keep someone engaged for long....After all the content in GT5 and even GT4, I expected so much more and, while they may well deliver it in future, the current content rates low...maybe in 2 years I will come back and give it a 10, who knows;
Ease: 2/10. The minute you start the game with a tutorial, being the first for a GT game that I am aware of, you realise that this a game aimed at the masses of casual fans rather than the GT fans. As you progress through the levels, bar the odd event or two, you feel that the game has really been made too easy....With GT5 I am unlikely to ever get 100% as some events are too difficult for me, whereas GT6 has been 100% complete for some time. The licences are a perfect example: Each test was completed after 3 or 4 attempts maximum, in GT5 some events took me an hour or more to do and there are still 2 that I can't manage after countless times trying. The game is crying out for a variable difficulty setting;
Sounds: 2/10. The issues here are well documented and historic. Sounds have pretty much stagnated from GT5....there was so much hope here which was not realised. Some cars sound fantastic but most, just, don't;
AD ("AI"): 2/10. Well, I don't think anyone can call them Intelligent so I prefer to call them "Artificial Drones" as they are pre-programmed drones. These are both disappointing yet expected but the hope was always that PD would come to their senses and give us racers to go with the races but it was not to be.
*I have not included online as I don't race online and have not tried.
Overall this is a solid game but, asides from a few things, not breathtaking. As a stand-alone game, I would probably give it an 8 or 9/10: It is longer than some games I have played (I remember one on the PS2 that took me 6 hours to complete it) and is an entertaining game. The problem with it is that it isn't a stand-alone game, it is the latest in a series and it falls considerably short there: I would compare it with the most recent Fast & Furious film.....a good film if viewed as a stand-alone film with plenty of action to keep you entertained but, when viewed as a part of the series, it just doesn't hold up as it has gone from the street racing concept that made the original famous. GT6 is a graphically beautiful game that doesn't do the series the justice it deserves.
In time it may become the game it cries out to be but, as it stands, it falls short.