A congenial person is easy to get along with. If you're trying to decide which of your friends to take on a road trip, choose the most congenial one.
Congenial means sharing the same temperament, or agreeing with your temperament. You can talk about a congenial person, place, or environment. Maybe you enjoy the congenial atmosphere of the library. Or perhaps for you the disco is more congenial. As you might expect for such a vaguely approving word, there are many synonyms: agreeable, pleasant, delectable, delightful, enjoyable, and so on.