got that mixed up at first, too,
basically you’re competing against your own previous review scores,
except for the early game phase(first garage games).
if your last game scored a 8.0 even, you have to do a bit better to get 9.0 etc.
(the tables in above link work easily for the garage phase but things get more complicated once you get the first “real” office, their skills/experience and workload influence the (internal) and review score as well)
You are competing against your previous game qualities, as others have stated. However what they forgot to mention is you cannot achieve a perfect 10/10 without having specialists. You need at least one specialist(engine,graphics,ai, and so on), but the more you have the higher quality your game will be. I have covered sliders, and engine parts as well in short videos, both of those also effect your game quality.(The videos are in the showcase section if you are interested.) All of these add up to compete against previous scores. But keep in mind, you can’t score 10/10 without having at least one specialist.
*Also, you aren’t competing against your last game, you are competing against your highest scoring game’s quality. If that makes sense.
I understand, thankyou… that’s discouraging to say something. I have six employees, three design specialists and three technology specialists, and still, you get 10 points less and the game goes from 9 to 6. Still, I think I may have to start configuring the sliders…
Check out my slider bars guide, it may show you something you have been missing.
I am getting to understand that the “all the time the three sliders at its fullest” is not the right strategy…
it really depends on what specialist you assign to what part(medium games and up) of the “workload”,
their actual skills(T/D ratio) seriously affect the tasks they’re given.
dragging a tech specialist(eg. T 750, D 200) onto something like Story won’t do you any good etc
The specialists I am talking about are the topic specific specialists. Like AI specialist, or graphics specialist, and so on.
Yes, that’s what I have 
Best of luck on you Game enDEVors!
You made my day with that post, thank you.
Good luck in your further ventures! 
I’ve only gotten one perfect game, which was a medium casual game (pokemon), back before i didn’t know much about the engine. since, i have not been able to recreate the perfect game.
I had a giant 2500 design and 1900 tech on a 10th sequel fantasy/rpg game and had a record on design and still had a 6 7 7 8 which is a 7 and still don’t understand why. All of my workers were specialist and all of them worked on the areas that they should. Had 3 guys that have mixed design and tech, 2 specialists on tech and another 2 on design.
For a perfect 10 everything needs to be well… perfect.
With 2500 Design and 1900 Tech you had a T/D ratio of 0.8 and for RPG 0.6 is spot on.
Should had given you a higher score then 7 though, But…
Most likely you had a very high last best game score.
And this game just did not improve enough to get a high score.
Now for your specialists, there would need to be 3 specialist which are important for the genre.
In the case of RPG thats: Story, Dialog, Gameplay, World Design.
You can also ruin your game by having too much of unimportant sliders.
For RPG thats Engine.
Last thing what could have been the problem: Graphics level. For AAA games you need at least 3Dv5 , anything lower will mess with your score.
I remember getting a 9, then a 4 then a 10, then a 3, then a 1
WTF?
Update (remove the 4)
what do you mean by AAA games ? (sorry I am noob)
AAA games are the biggest game you can make in the late game. ( Small > Medium > Large > AAA )
In real life games like Call of Duty, Starcraft, GTAV and so on are AAA games.
I created a copy of “Game Dev Tycoon” in the garage, with 2D, and mono sound and earned a 10’r (No cheats used, with 8 previous games), So it is POSSIBLE 
It’s probably only possible to do it with that topic/genre and name as a head up to the real reviews of GDT : P
Names do not have anything to do with the game. It’s just a bit of realism. 
I was once in the garage for longer than i was supposed to be, and i got a 10/10 game.