Well, being a huge racing and automobile fan myself, Forza 3 is currently the best racing experience you can get on consoles, but it's far from an Arcade game, even if you tone it down to a more simple level ;)
It has tons of room for expansion, even if you start out at the simplest level, as you'll gain experience in departments that you couldn't gain in arcade racers like Grid our Burnout. It all comes down to your brother preferences, which seems to more into those kind of games.
I hope your brother enjoys the game and that he doesn't give up if he faces attrition in the game, it will be worth the struggle for him if he carries on with the game.
That being said, I need to get back into the game, to finish Season 6 properly XD
Current PC Build
CPU - i7 8700K 3.7 GHz (4.7 GHz turbo) 6 cores OC'd to 5.2 GHz with Watercooling (Hydro Series H110i) | MB - Gigabyte Z370 HD3P ATX | Gigabyte GTX 1080ti Gaming OC BLACK 11G (1657 MHz Boost Core / 11010 MHz Memory) | RAM - Corsair DIMM 32GB DDR4, 2400 MHz | PSU - Corsair CX650M (80+ Bronze) 650W | Audio - Asus Essence STX II 7.1 | Monitor - Samsung U28E590D 4K UHD, Freesync, 1 ms, 60 Hz, 28"
