Disclaimer: Been with PCars since the beginning (what...nearly three years ago?)
Driving comes in a number of fashions...and they pride themselves on different things. Luckily for us, this means everybody wins.
Where Forza and GT are more aimed at money-making and car modding with hundreds of cars...you then have iRacing with relatively few cars aimed solely at motorsport simulation (same with the RFactor crowd etc.). You have some silliness like Driveclub etc. but those are just what they are.
This is where I think PCars and to a lesser extent, Assetto Corsa hit the nail on the head. They took a swing and cracked a shot straight down the center. Following PCars it's been ridiculous the changes from start to finish...and I do think they aimed a little too high in some areas, but overall the PC game is pretty darn solid.
AC/PCars hit that median between super-mega-sim...and enjoyable racing game. I think PCars took the right approach allowing the huge amount of customization to really cater to the type of player. I can't think of many racing games with so many options
-Deep graphical options/adjustments
-Tons of control adjustment
-AI skill/type/etc.
-Weather (random slots, advanced timing, etc.)
-Time (when and how fast)
-Sound adjustment (this didn't end up being as detailed as they said they'd allow)
-Control of penalties
-Control of restrictions for room entry
-Adjustment of damage, fuel, tire wear
They went after so many options I think this is why you see it more buggy than most titles (if I'm honest I haven't encountered many bugs in the release - other than the pit stop bug that 1.4 caused). They're trying to do a ton o' stuff and it shows on the Xbox/PS console releases since they didn't have any of the quantity of playtesting they benefited from on the PC version.
AC has slightly better physics but (sans mods) is way too sterile with even worse car selection and the poorest track selection in any racing game I've seen. While mods are nice, I play with a big group of guys and we can't be bothered with verifying everyone has all the same mods/tracks/cars etc. I think AC could have been huge, but for all around enjoyment and letting me race how/where I want, PCars definitely takes the edge.
RRE could have been huge to me, but the micro-transaction model killed it dead immediately. My buddy and I downloaded it on Steam...looked at the costs/market and immediately uninstalled it. Good as it may be (with the best sounds in the industry by far) it'd be $400+ to get all the tracks and cars (of which there are about enough to warrant a full PC game). Shame as I love Simbin and had high hopes.
PCars issues (my opinion):
-Crappy cracked glass effects. For a game with great graphics...this was weird that they released it that poor. Rain effects were sub-par but they're introducing speed effects so that'll help immensely. Unless you're behind someone, there isn't a real need to turn on your wipers most of the time.
-Sound is crap. Okay it's better than say Forza and probably GT...but is one of the weakest points of the game.
-Customized classes are not available. This is a huge killer for me. We normally run 3-5 players with 10-15 AI. Because of the silly class organization, some classes have far faster cars and some have far slower --- I can't pick what the AI drive, nor can we eliminate slow cars from classes. If you run the Group 5 class...the Mustang TransAm and Mercedes DTM are heaps faster than the other cars, so if we all want to run some fun Group 5 cars without running a spec-car, we can't determine if the AI will be 5-6 seconds a lap faster. This is frustrating. SMS stated they can't run more than 8-10 types of cars on the same track without memory issues...I'd really, REALLY like to be able to make a custom class --- this would also allow multi-class races online (not available at the moment which sucks for LeMans stuff)
-Car selection*. I'll be honest, I love the variety. However, due to license issues there are many cars which have no competitors. So, outside of a spec-race you're not going to have a good race with someone. Most cars have at least one proper opponent, but I'd have preferred to see licenses aimed at ensuring 3-4 types of car per class when possible. I do love that each car has a very unique feel (this may be because I'm using a wheel for the first time in racing, but it's a nice change from Forza where you had about...6 different "types" of cars).
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Cliff's Notes: It's an excellent game that is modular and adjustable to fit pretty much every driver...unless you're just into paint schemes (which you can do) or earning money.
*Some of this is being alleviated by the cars coming out later. Having seen all of the current license agreements I'm fully satisfied with the "end" number of cars/tracks we'll have access to.
