Popularity in terms of TEAM sports, not individual ones so I will be excluding Racing, MMA, Tennis, Golf. And their current National trends.
In the US: (as someone mentionned above)
NFL: Popularity Highest it's ever been and strong growth.
College Football: Strong constant growth
MLB: Lowest it's ever been and still constant decline, Fan base oldest of all pro team sports.
College Basketball: Growing
NBA: Upward trend, down from the 90s and the Jordan era
NHL: Upward trend, down from the early 90s.
MLS: I don't have enough Data
In Canada:
NHL (And everything Hockey related, IIHF): Highest it's ever been and still very strong growth
NFL: Some growth, the Superbowl is a huge atraction. In general FAR behind hockey.
CFL: Strong growth, much more mediacised in recent years.
NBA: In general stagnant
MLB: Constant decline
MLS: Strong growth with new expansions coming to Vancouver and Montreal. Expect it to surpass MLB within 5-10 years.
North America in General:
NFL
MLB
NBA/NHL: Can surpass the MLB in the next 5-10 years if trends continue
MLS
Once again, this is based on the popularity, TV Ratings, Attendance of all these sports. NOT the Revenues alone they make off major TV Contracts.
The CFL gets higher rating then the NFL in Canada....and is subsequently more popular
NHL
CFL
NFL
NBA
MLB