What Racing Games Should I Get?S

For Christmas, Santa Claus bestowed an Xbox 360 to my good little children (they're all little girls, no need for one of the new systems). I have seen quite a few of you stating that you play games on Xbox Live against each other, and this non-gamer wants in. I have some questions.

As the title states, I need to know what racing games are the most popular for the Xbox platform here. I'll probably go out and buy a couple for myself in a few weeks. No rush, though. Work has been busy and my young children/wife keep me occupied for the vast majority of the remaining waking hours that I have.

Also, do the games you play allow for vocal interaction? Do you have headsets that you can chat with each other with? That would be a lot of fun in my book. If so, does anyone have any suggestions as to a good wireless headset that I could use?

I'll buy a first person shooter as well (probably COD Ghosts), but I'd love to jump on with some of y'all and rip up a virtual track or two. So please, enlighten this old fart a little. I promise I won't talk too much trash during the races.