As opposed to the best car God has ever made?
Let me make this clear: cars we see today are result of years and years of evolution. They may seem complex and beautiful from the outside, but most of their internal parts are decedents of simple machinery from centuries ago. And while we're on the subject, let me propose that cars, trucks, bikes, trains, even air planes are all either directly and indirectly related to each other, mechanically.
With that made clear, back to the original question: best is very subjective. One may find a big soft luxury car the best ever, while other see a record breaker speed machine as best, or even regard a go-anywhere off roader as the best for its practicality.
Though if it were the question of 'Greatest car ever made' I'd vote for Ford Model T. If you need to ask why, you're probably too young to see beyond posters and performance figures.