Wii Sports
"Wii Sports" includes boxing, bowling, tennis, golf and baseball. The games require a great deal more physical effort than traditional hand-held controller games, but their main purpose is entertainment, not physical fitness.
Wii Sports Resort
"Wii Sports Resort," a sequel to "Wii Sports," was released in 2009 and offers 10 games in addition to the first five: swordplay, wakeboarding, Frisbee, archery, basketball, table tennis, power cruising, canoeing, cycling and air sports.
Wii Fit
"Wii Fit" is a physical fitness game that offers four categories of activities: yoga, strength training, aerobics and balance. Each category contains numerous exercises. Though "Wii Fit" is designed to be entertaining, the main focus of the game is physical fitness.
Similarities
Both games are far more physically demanding than nearly all other video games. You can get a good workout with either of them.
Differences
"Wii Sports" emulates popular sports games, while "Wii Fit" provides video-simulated training and assistance in physical fitness. "Wii Sports" is entertainment that includes physical activity; "Wii Fit" is physical fitness that includes entertainment.