I am very disapointed in Project Cars. I own the PC version and that game did not live up to the hype it set. Its not a bad racer but Turn 10 pretty much out classed PC in all aspects. I played FM6 demo and i was blown away with the entire package of the game where as PC was more a let down. Only good thing about that game is that it has a 4k option ready for my next TV. FM6 has better physics and sound from my experince and to top it off FM6 actaully looks better with more cars on screen. I honestly dont know what else i can say. With its console limitations, Turn 10 out-preformed a game designed around PC hardware. I am impressed. So far FM6 is the best Sim racer i have played since FM4. I will be looking forward to seeing GT7. Hopefully they can create an even better racer since they have had alot more time. The bar has been set high, lets see who can beat it now.

T10 is more like an overseeing entity. They work on the next FM on the years off.

Forza Motorsport is a Sim first. This infatuation with weather on racing sim, comes first from people that are not a big fan of the genre.

It's just like rain in soccer, it was cool when it was first implemented but it gets tiring after couple of matches.

Forza has been the king of racing.

Forza is not a racing SIM. Project Cars is at the moment the only racing SIM on console. That will change next year with the arrival of Assetto Corsa though.

console games just have had to be too accessible to be true sims. This is at least partly due to their need to be easily playable with a controller.

This has been common knowledge to sim racers for a very long time.

What are the requirements for a Sim game? What does Forza needs to do to become a Sim?

Assetto Corsa allows the use of gamepads, easily.

I think that Forza series has been the best racing sim I have played. I could never get into GT when I had Forza to play. Before Forza it was all Need for Speed and Midtown Madness for me. Project Gotham Racing was a great game as well but It still is Forza for me. I played F6 demo and can not wait for the game. I wish I had more time for games this fall since I will be playing so many, F6 will most likely have most of my hours followed by Halo/Rainbow Six.

Edit:

But for OP's question, No. No forza games have came out for PC yet, so why would that change?

To be more realistic and less arcadey ;)

You do realise it rains in real life right? And races take part in wet weather require different race strategies and driving styles? This is what big fans of the genre want.

It's not really a Sim racer, more a "Sim-Lite" as far as realism and physics  go.

It rains in real life?

Sure rain rquires us to change racing strategy. Like I said, it's for couple of races and forgotten.

What game on console is a Sim racer and not a "Sim-Lite" or whatever that means.

More realistic physics mostly. But I don't ever expect Forza to become a full blown sim because that's not T10s goal. They aren't trying to make a simulator and they don't.