Long term investing success is built on "process" i.e. tripling your money on a junior mining stock does not argue for longer term success.   A good "process" involves more than just owning stocks in one very narrow sector.  And what has worked in the past is hardly guaranteed to work in the future, etc., etc.

The Canadian banks are a very profitable oligopoly (mid teen's ROE's, if not higher)...but they are still banks...and in a real crisis are vulnerable.    

I own several, personally, but I am also cognizant of what happened to many to most of the US large cap banks during the 08/09 real estate/financial crisis meltdown.   Canada largely escaped that (but there was a real fear that CM and/or BMO would be pressured to reduce or eliminate their dividends), but there is no guarantee that we won't get whacked in the future.  

 I will continue to own my Canadian banks...but I would never make them 100% of my equity portfolio.