Some fun NBA games to play online are "NBA Shootout" and "NBA Spirit." Both games offer multiple levels and are available to play online for free, as of 2015.
"NBA Shootout" is a fun version of shooting hoops. As an NBA player shoots free throws, the players shoot different types of guns to destroy the ball before it makes it into the basket. When the player gets enough points, a new type of gun appears.
In "NBA Spirit," players attempt to sink baskets in front of a crowd. A small basketball appears on screen and slides back and forth under the net. Players must shoot the ball when the basketball is underneath the net.