Nice classy style, lots of little details is what I like. Nice rims (big) and sitting nice and low. Maybe a screen in the dash, good sound. Parts that not everyone has or has even thought of putting on.
The best car can't be a sleeper because a lot of people (if not the majority) like shows cars as well. So if there is such a thing as a best car ( which there isn't ) then it would need the best of both worlds, in other words all show and all go.
i agree with mart , everyone has different opinions with there cars . some like them fast , some like them low , some like them some like them nice ... everyone's opinion is different !