Wow it seems I brought some bad discussions by mentioning steamcharts figures in my previous posts.
It's just a way to estimate the popularity of a title IN COMPARISON with others and to estimate the potential of online gaming of a title. By no way it is an accurate tool to make a deep analysis.
What it just shows is the average number of people playing a game at the same time within a specific period, and not the number of owners of this game.
The most valuable information here is that sim racing titles are not played by many people at the same time in comparison with other genres. It shows that if you are not in a league you will have difficulties to find races with the category you want to race in.
A title with less users connected at the same time is less appealing for online races than another title with more users. But it's only theorical because you don't have any indication about the number of people, among the connected ones, who are racing online and offline.
A 300 average of users connected at the same time shows how much sim racing is not as popular as other genres. In the multiplayer FPS genre this figure would just mean a dead game. But multiplayer FPS users move fast to the next title. Sim racers like their sim and use it several years (just search for the mods for F1 challenge, there are still active modders on this game). This can explain the relative stability of the figures of the simracing titles in time, although they are low.
To make a point, take the example of space hulk deathwing. Deathwing, a FPS coop title, has been a failure with its first release, with a decreasing number of players, dopping to less than 20 average. You were just not able to find people to play with, the game was useless online. Since the release of the enhanced edition, failing to bring new players but bringing back former disappointed users, the average has been stable to at least 50 players (the game managed to bild a tiny community). And I've always been able to find an online game (requiering 4 players idealy) even with such a low number (ridiculous for a FPS game). So stability in time of the amount of players connected at the same time is also important.
Interesting data would be the number of new owners and of quiting users each month, the average of launches of the game during a month and a full year by unique users and the variance...
We have few information, we can only use them as tools to compare titles' popularity, keeping in mind their lack of accuracy, and without trying to make some interpretation which would be based only on speculations (as comparing the steamcharts figures and the number of voters in this thread).
Well sorry for having brought that subject, have a happy new year!