As a mommy of 2 boys, I can attest they are just wired differently. The car obsession gene is not a myth. From about 9 months old both boys smiled from ear to ear when they saw a car, truck or construction equipment. All things boys.
Around 1.5-2 years old, they made the nature progression to trains. Thomas the Tank Engine, you fill a void that cars can't reach.
And now at 3, Superheroes are the answer. For now, Batman & Spiderman are the faves. Guess what Halloween costumes we're interested in!:)
After pumpkin picking, our 5 yr old friend introduced us to Star Wars. While a little advanced for a 3 yr old, he still liked it. (Although I'm not sure he fully understood what was going on in the 15 minutes we let him watch).