Depends on what you're looking for...
Toronto and Montreal are dynamic cities full of culture and things to do but can get uncomfortably hot and humid in the summers.
Vancouver is a very beautiful city but has expensive housing.
Calgary is a nice mid size city which has grown lots recently but still lacks the culture of the big eastern cities and is going through some growing pains. The beautiful Rockies are only one hour away.
I'd look into those 4 cities for starters... Good luck!