If you're on Xbox (I know you aren't but who knows what Black Friday brings?) it was recently a Games With Gold title so you may already own it, but it's got everything: a really old school arcade driving model, insane speeds, 200 tracks at launch, an incredibly deep and versatile editor (that can even automatically generate tracks for you), tons of gamemodes including hot seat, split-screen, online, an innovative Double Driver mode, minigames akin to Mashed and so on. Do you want an all around arcade racer with massive speeds, stunts and no pretense of realism? Try TrackMania: Turbo. You can probably pick up the latest one for like 30 bucks on Black Friday, but if you want to be sure you're not wasting money you can probably find F1 2016 for even less to get a quick look at the basics. The driving model is very scalable and there's plenty of skill ceiling if you want to get fairly deep into it, albeit it's still very arcade-y. Do you enjoy the complexity of racing (tyre wear, fuel usage, pit stops, etc.) but don't want to get invested in an insanely complex driving system? Codemaster's F1 games should fit the bill especially if you're a Formula 1 fan. The Forza games are the greatest of the gen but you already knew that, so as for other racers it really depends on what you're looking for. It's still full of glitches and technical hiccups, too. Project CARS is an unforgiving simulation, so if you're looking for something more relaxed it's not a good buy. It really depends on the kind of racing experience you want. Its my racer to go until Project Cars 2 gots better and I can alternate between the two games.
If you have the itch for a good realistic racer and you have a PS4, GT Sport has a good sale in the PSN and currently is far more polished, its a excellent package and in December a big singleplayer update will be released. Its baffling how the game got the good reviews (at least in consoles), considering the state it was released.
So I would wait for more patchs and user impressions.
They released a free demo yesterday, you could try it, its supposed to have a newer version of the game but I haven't tried it (as far as I know there's no patch or date announced for the full version). I bought it day one with a lot of hype and I was very disappointed, and specially after two months the silence of the developers is kind of worrying. And the online works also very uneven, some times you have a lot of disconnections that lower a lot your driver rating. The game has good foundations, but they released it rushed as hell, there's been only a patch and the game has a lot of bugs, the thing is some races or events are fine, in others the IA and physics are messed up, its a very uneven experience (and a few problems with the HUD and other things that are incredible they passed QA testing).