That's the same as the 14 million for Forza. Point is how can Forza really be number one when the crew alone has close to the same number of unique players. Forza is only number one in releases.
Because The Crew is on 5 platforms and was given away for free on 2?
The Crew had over 3M on GWG alone, add in when it went free on PC maybe another 1-2M, and you're looking at 14M vs 5M sales maximum (well I guess this isn't necessary true as people might have downloaded it and not played but 3m+ isn't anything to scoff at... even less due to preowned etc). The Crew was also on 5 platforms (PC (Steam+Ubi), Xbox 360, PS3, PS4, XB1) vs for the most part 1 platform (360 for FH2 & Win10 store for FH3)
The crew did very well but it's easy to see why Forza's number is more impressive, and if you don't think so then idk what to tell you.
Also you kind of answered your own question, "how can forza be number one when the crew alone has close to the same number of players"... well, as you said.. close but not more than.
Not saying forza is #1 and tbh I don't really care if it is or isn't, but the crew is hardly a fair comparison with unique players even though forza still has more