http://en.wikipedia.org/wiki/List_of_video_games_exclusives_(seventh_generation)#Microsoft_Xbox_360
Not like FM3 is the ONLY exclusive. Heck, in the racing genre you've got FM2, FM3, PGR3, PGR4, Race Pro, and Indy 500 Evolution as exclusives (well, Wii has an Indy port as well...). That's not the full list of racing games, but ones I'd recommend. Even "arcade" racers can be a blast - can't be a racing fan without some arcade action. Likewise I'd recommend to 360 owners getting a PS3 to grab GT5, F1CE (yes, it's on the PSP...), Ferrari Trofeo (yes, it's on the Wii and a bit of a dog, but it's a pretty good game - can't beat the Ferrari sound).
And both consoles have a ton of non-racing exclusives that are AAA quality. Of course, the best of all worlds is to have all 3 consoles (which I do). It gets you away from being a console whore. There's no reason, other than $$$, for a PS3 owner not to buy a 360, or a 360 owner not to buy a PS3.