The one thing Top Gear has is a female audience. My wife is not interested in cars at all, yet she can watch an episode of Top Gear.
That is actually a good point and reinforces my opinion that the show is entertaining beyond its subject matter. My wife actually is a "car girl" but I think she enjoys the show as I do -for the often breath-taking footage and the frequent belly laugh.
Regarding a favorite episode... I was reminded last night of mine. It wasn't even really a car theme but rather two-wheeled -the journey through Vietnam on scooter/moped/bike. Watching Clarkson hit the road still brings tears to my eyes.