Regardless of what the website says, I am pretty skeptical of the 900 players online in FAF. That said, I am just looking at what other gaems on Steam has. Sins does around 1,500 and it sold far better than SupCom did.
And really, according to the FAF page, they get 2,800 players PER DAY. So not sure how ou can get 300 people being online unless a lot of people are leaving the lobby up 24/7.
900 Players is the high mark that is only achieved during weekends. Did Sins really sell better than SupCom if you include all the physical copies? I have my Supcom because I bought it in a store when it was brand new, did Sins ever have a physical release? I think what really makes the difference though is that Supcom especially through FaF in the end has a stable and loyal multiplayer playerbase. I personally can say that I like Sins but I'm not feeling a draw to come back time and again as I do with Supcom at least not for multiplayer which in and of itself might stem from the fact that its hard to find any open games.
If you compare the number of games that are open in Sins Multiplayer vs FaF you see a significant difference. Apparently according to steam stats there are roughly 500 players in steam alone playing sins right now but the ICO multiplayer has 50 people online. So maybe Sins is just much more interesting from a Single Player perspective?
I'm sure a lot of people Idle in the lobby, but right now for example there is 267 People in the lobby which will probably go up to 500-600 at least in the evening (GMT + 1 here), in general I get the feeling most FaF players are probably EU but maybe thats just because they play in my timezone.
Seeing how during a good evening there are about 15 open games at a time I'd say its rather full if you include the number of games that are approximately in progress during that time as well.
If Ashes reaches and holds that number I'd be happy enough, its rather easy to get into FaF games imho.