Recent research suggests that virtual reality (VR) games can engage players in physical activity with high levels of enjoyment. Understanding users’ motivation to engage and enjoy immersive VR exercise platforms is thus important to designers. We designed a VR exercise platform and conducted an experiment with two conditions, one with a static user interface (UI) and the other with an open world environment. Across participants there was significantly (p = 0.03*) greater enjoyment reported in an open world compared to static UI. Enjoyment in both static UI and open world conditions was positively correlated wih user’s psychological needs and experience; autonomy and immersion. Participants’ future play intention was also predicted by autonomy and immersion, but only within the open world condition. Our findings also suggest players can be classified into entertainment-focused and exercise-focused with different expectations and therefore different engagement behaviors with each VR exercise environment. The study highlights the value of informing VR design with measures of psychological need satisfaction.