Back to Basics

I did some quick painting using reference from some sci-fi show, Trek Wars or something. All kidding aside, "Firefly" has some great lighting samples thanks to the show using practical lights in the scene rather than blown out stage lighting.
Spent maybe an hour or so on each of these, I wasn't too focused on likenesses, but they ended up more or less looking like the actors. Why is it when I try to make it look someone it takes me twice as long?