Forza Horizon 4 is very fun, although a bit flashy, marketed to teens and at times annoying. The car sounds are just horrible in FH4. I don't think I've seen a game that has the proper RB26DETT engine sound from a Nissan Skyline GT-R R34, and that bothers me a lot. Kills a lot of enjoyment. Plus, the sounds are a bit flat and possibly over-processed anyways.
My bro picked up an Origin/EA subscription and gets to play the EA catalogue at a laughable price. And while he picked up Mass Effect, I picked up NFS Heat.
And boy, does it look like NFS has finally made a good one. First of all, we need to compare it to Most Wanted and Carbon (which were peak NFS). You have driving by day, driving by night, a modest map - not too large, not too small - with enough different portions. Customization is even better than in MW/C, because you can even do engine swaps, change the way your discs/calipers look and whatnot. Driving is almost like MW/C. Arcadey, fun and forgiving, but not overdone. Challenges and races seem fairly standard, albeit there are ones a bit more nuanced. I didn't really care about the story (besides MW), so I won't really bother with it here - also because I haven't went through most of it. MW did feel a lot more fun, but let's be real here, it's pure nostalgia factor for me. If I didn't have so much fun playing it over the years and compared those two games now, I'm not sure which one I'd pick as a favourite.
Secondly, we need to compare it to Forza Horizon 4, because it is its main rival. And to me it looks they just knew what was wrong with FH4 and made NFS better by not repeating Forza's mistakes. Namely, it's not too flashy and it's not really marketed to early teens (with the crazy outfits, bright-coloured in-game signs, loud music and whatnot). The engine sounds are much better (and slightly adjustable), which is a huge bonus! Microtransactions seem completely absent - you have money, and rep - one buys you stuff, the other unlocks it. You win money on (legal) races by day, you win rep on (illegal) races by night. So you kinda have to do both. The only thing I've found you can buy with real money are a map (with all the locations) and maybe a special car or two, which is perfect. The driving seems to be improved too, though I've yet to drive faster cars, or offroad.
Where FH4 is better is the actual world where you play the game, because the map is much bigger and much more beautiful to look at and drive through. Besides that, the challenges, although at times chaotic and frustrating, were a bit better, mainly because you had to do some stunts or deliveries etc, much more creative. And the graphics were a bit more balanced; sometimes in NFS, at night, it's hard to see where you should go because of the lighting. And last but not least, the car list was much, much, much, much more expansive. But it does have the car that matters, hopefully with a better sound than in FH4 (see above).