For me - the peak of racing games ended with Forza Motorsport 4. Everything since has been terrible. Even Forza Motorsport 7 is way more enjoyable than GT7.
With Forza - EVERY vehicle is purchasable from the beginning (that is, if you have the credits saved up to purchase it.) So if there is a car you want, you can work up to buy it. It makes you want to actually progress in the career mode. Forza has way more vehicles. I love super cars, don't get me wrong. But being able to buy and drive a car you own in real life? Forza may very well have your personal car in the game!
Gran Turismos selection is miniscule in comparison. They also seperate the cars. You have a severely broken "used car" market that gives you some older, but affordable cars. But this list never changes. It's the same cars all the time. Outside of the used car lot, you have "brand central" where you can buy brand new cars at insanely expensive price tags. Your credits do not go as far as they do with Forza. Your car collection on Forza can grow tremendously. Gran Turismo makes you grind, grind, grind to get just one car.
The customization with Forza is superior. Window tint, liveries, custom paints, wheels, etc. So much better with Forza. With Gran Turismo you can't even tint your windows. On Gran Turismo you also cannot see what your current selected car will look like with a custom paint. The game gives you a template for the paint - who designed this?
Tuning is a nightmare on Gran Turismo. The wheel spins compared to Forza are an absolute joke. With Forza, you can wheel spin a whole car. With Gean Turismo, you might win an engine for a car you don't even own. LOL.
Gran Turismo driving physics are horrid. Borderline unplayable. I swear driving a car in real life is easier. Maybe it's a controller issue, but I swear your steering wheel doesn't respond to input. It's like the cars only know how to go straight in this game. Also the first person view looks terrible. It's like you're sitting in a stationary cockpit and the environment moves around you like you're sitting in a simulator with a big screen. Same can also be said for 3rd person. It's like you're "steering" the world underneath the car. And not steering the car within the world... If that makes sense? Your car feels like it's stationary and the world moves underneath/around the car.
The menus are so clunky and frustrating to navigate. The "Cafe" career mode is hilariously terrible. There's no story line. Just race, race, race. No real progress or reward system for progressing through the cafe career mode. You get some cool car history when you complete a "menu" but that's about it.
The visuals aren't even that good. I don't understand the praise. Forza looks so much better. The cars look decent, but the environment looks PS3 era. It really takes you out of the immersion when you notice the backgrounds and how some are even 2D.
The engine sounds are terrible. This is nothing new with Gran Turismo. They don't even attempt to make the cars sound realistic. This REALLY kills the immersion for me.
The sound track is repetitive and abysmal. Classical music for racing? Come on. It's like they intentionally made this game horrible just to mess with actual car enthusiasts.
Want a short and sweet review? I've had more fun with LAWN MOWER SIMULATOR than this poor excuse of a racing game.