rFactor, but when i'm not in mood for racing, i love to play OpenTTD (opensource successor to Transport Tycoon Deluxe) - made in 1995 but still awesome .
Have you tried Project Reality on BF2? It is a bloody good mod which forces team work and tactics. The vehicle respawn times are much longer (up to an hour for some), weapon kits have to be allocated by the commander (you need a driver kit to drive heavy armour, aircraft and such, as a squaddy all you can drive is the Landy).
It is hours of fun. Although it can be a hassle finding a decent server to join.
I mostly play racing games since i hate most of the moder shooters.
I like games with stories Like Bioshock.
I also have a heavy dislike for RPG's so for me ist racing story game or some arcade racer like PGR.
But there is one game besides LFS that gets played often its The Sims2
I also love to play some rfactor ever now and then some Richard burns rally some Enthusia Proffecional Racing(ps2).
And I play forza sometimes
If it was not for LFS i would be spending more time with.. Chess (PC & real stuff) Supreme Commander & the Total War seris of games.
On the flip side of the gaming coin lies my other favourites
Quake HL & UT seris of FPS stuff.
I like to think LFS combines a liitle of both the control and adrenalin that FPS and RTS thrive upon.
I'm playing a little FPS game called Special Force here, and called Soldier Front in other countries. Actually I play it more than LFS, because, well, you WOULD get tired of BL1 for a year, right?