Yeah should have rephrased my statement - the Bills have not been a success here. Most of the Canadian NFL fans don't really have one team they follow - it's really spread out. You'll have bandwagon fans hopping on the Seahawks bandwagon, Patriots fans, Broncos fans, Giants fans, 49ers fans etc. There really isn't a team loyalty.
Can an NFL team thrive here? Possibly. First a new NFL stadium would need to be built - they can't play at the Rogers Centre (lets be realistic). A new stadium likely needs to be build outside of the city like in Vaughn or Mississauga. Also, I'm sure it will be a huge fad in the first year, but if the team doesn't have success for an extended period of time, you're not going to get 80K at each game.
Also, like said before even by NFL people, if an NFL team moves to Toronto, they need to make sure that they can co-exist with the CFL. They can co-exhist.