The history of Alberta actually shows Edmonton and Calgary trading places several times as the premier city in the province. It's only in the last 20 years that Calgary has really pulled ahead.
Edmonton has also traditionally been much more politically liberal than Calgary, which might appeal to some people - during 40 years of Conservative power (under various party names) Edmonton was often swept by NDP candidates, usually the only opposition members in the province.
Edmonton also has an excellent Drama scene - one of the first Fringe festivals outside of Edinburgh (and still one of the biggest), a great folk music festival, a vibrant multicultural scene without excessive ghettoization, and a 1-2 km wide river valley park that bisects the city with walking and biking trails.