I recently discovered this GTA San Andreas mod for Battlefield 2. Barely ever played any BF, never played BF2, but watching this gameplay sold me on this mod immediately and what I've played so far has been awesome fun.
Some voice lines are jank and obviously generated with AI, some weapons have weird viewport models (thumbs are freaky sometimes), and I absolutely cannot get the hang of sniper scopes or flying helicopters. But it's a lot of fun, and it is EXACTLY what I was hoping for when I saw "San Andreas in Battlefield".
Download in the video's description, comes with Battlefield 2 as part of the package so no need to hunt around. Don't know if Multiplayer works properly, BF2 looks like one of the early games to want you to have an account for some online service (which I'm guessing no longer exists), so it might require some fucking around with/further 'modding' for Multiplayer to work.