I love multiplayer games. Very little beats the feeling of taking on real people and working with real people in a game. People provide much less predictable challenges than computer driven opponents.
One thing that many multiplayer games miss is a good story. This isn’t always true, but the deepest narrative experiences tend to be single player only. Think about games such as Walking Dead, 80 Days, Heavy Rain, Her Story etc. Each of this offers a deep story, but on the surface seems to offer nothing that resembles multiplayer elements.