I'm fairly certain that the PS Plus subscription numbers have already grown far beyond 5m after the Destiny launch. Plus they will likely grow alot again after DC launches.

Forza as an exclusive, The Crew if you're talking multiplatform.

The above is retail-only, of course!

The crew and forza

I believe Forza Horizon will sell more than Project Cars. DC numbers will depend on the reception the game gets.

I have no idea, I'd say on of the multiplats, but the crew doesn't have much hype and the previews aren't great.
PCars has had no marketing, which could kill it.
Drivelcub sales won't be huge because of free plus edition.
Horizon 2 also available on 360. If you counted 360 sales then I would say that, but then again, the crew is also on 360.

It's too complicated.

Forza Horizion 2

I think project cars will be best selling on every platform. Simulators have the potential to sell much more than non-simulation racers like FH and DC.

I think The Crew because it's coming out on both platforms and Project Cars is mainly focused on PC, and the people interested in Project Cars will get it for PC. So my guess would be last for Project Cars.

Driveclub will be near last because of the PS+ version. By this I mean unless it's really spectacular, I doubt many people are going to upgrade from a decent prologue version to decent sized game for €60 more.

I'll be using the PS+ Driveclub version as a demo. If I'm not engulfed, then no chance I'll be making the plunge of an actual sale. I also imagine there will be thousands of people also like me. But because of Sony's bundling and advertising, I can see it squeaking past Project Cars.

As for Forza Horizon 2, I see this doing extraordinary well, easily beating Driveclub sales and possibly trumping The Crew. So my list goes:

1. The Crew
2. Forza Horizon 2
3. Driveclub
4. Project Cars

I must be in the minority, but I have visions of The Crew bombing.

I think Driveclub will have the biggest userbase, but I don't think it'll have the most retail sales.. Project Cars is going to struggle a bit too I think, but only because the core audience for that will likely buy it on Steam where there is still a pretty solid sim racing following.

I think the marketing budgets of Forza and Drive Club will shout over Project Cars on the consoles.

Best at retail probably Forza, particularly if we only mean globally in the US.

forza horizon 2 on xbox 360 driveclub on ps4. the crew will bomb