I'd be happy if any of those leagues came to Montreal. I'm a sports fan first and I'm able to enjoy any of those sports.
I doubt basketball would work over here, but the other two would definitely have a chance. If I had to choose, I'd probably take the NFL because American football is way better than the CFL, but I'd also be ecstatic to get the Expos back.
I guess NFL , but Montreal is faaaaar down the list of cities the NFL would want to go.
So I guess the return of the Expos , i'm not the biggest baseball fan there is but since I lived not far from the Olympic Stadium I liked going to games and will certainly go if they return even in a new stadium downtown
EDIT: Damn , right now in Montreal it's sunny i'm outside with my laptop and god I would love to put a Expos game on the radio and drink my beer.Good times.
I'd like the NFL best, but it's way too unlikely. I'm not sure what the reqs for the stadiums are, but iirc it's over 70 000 people. The Big O can't have that many people in it. Quebec can't even get an arena without a truckload of BS from all parties involved, I can't see anyone agreeing on a 500M$ or such investment for a football field.
The NBA is the likeliest, because they can just go in the Bell and everything is fine. Though I'm not sure I'd want to see a Montreal version of the Raptors.