It's a huge time investment, but finally achieving pro status as a male player lets you compete against the likes of Federer, Roddick, Haas and Philippoussis, while the women get to challenge pros such as Henin, Mauresmo and Sharapova.
As well as the deep and challenging career mode, PS3 and 360 owners can also compete against others online. To compensate somewhat, the Wii version has bonus multiplayer party games instead.