...and what would someone be called who falls in the middle?
These aren't two ends of the spectrum... Utilitarian is a pretty even-handed way of looking at ethics and is therefore the most appealing to most people who don't have a strong opinion to begin with.
There is a huge range of ethical theories and ideas. There are ethical egoists (whatever is best for the self is ethical), there are altruists (whatever is best for the other is ethical). There are hedonists who argue that the only moral thing is that which brings pleasure.
