I spent a ridiculous amount of hours on GT1/2. Picked up Forza 2 when I got my Xbox. It's pretty fun, but like GT, a little bit empty.
I don't have Xbox Live Gold as until recently my internet connection was never good enough to make it worthwhile. It used to crap out randomly and I was getting a bad rep, people thought I was dc'ing from games because I was losing :(
I traded it in when I bought Magna Carta 2, I hadn't played it for months. The adverts on TV are insane, though. Computer graphics are beginning to freak me out, unless you look closely, they aren't any different from real life...