Without a doubt at its peak was 1967. A lot led up to this. Their rivalry in the 1940s, the early 1960s, the 1964 playoffs with a Keon hat trick to seal Game 7. Then came 1967. The Habs just as well thought they were winning the Cup and Canada's centennial was happening that summer. A Cup would have been a nice display. Who was going to stop them? This old Leafs team? They did.
Unfortunately there has been nothing noteworthy since then. A couple of lopsided playoff series and that's it. It is there in the hearts of the fans, but there has been nothing to cheer about.
^^^ Oh ya, Montreal was heavily favored to win in 67 and in fact Chicago which met the Leafs in the semi's same thing.... then Terry Sawchuk played a series for the ages, Bobby Hull still claiming to this day he'd never seen before nor since a more incredible display of goaltending. Absolutely won that series for Toronto and gave the team the confidence, the boost it needed heading into the finals against Montreal.
For most of the O6 era the scheduling fueled the Leafs / Canadiens rivalry. The Leafs had the Wednesday night home game, the Canadiens the Thursday night home game.
During the 70 game season the two rivals were scheduled to play each other 14 times.Since the two rarely played each other on Saturday night, the midweek game, weeks they played, dominated media attention. A back to back series of two games Wednesday and Thursday night was highly anticipated.
^^^ ya, Clarence Campbell in the late 40's thought television would be the death of the NHL at the gate and had to be carried kicking & screaming into the mid-20th century by oddly enough the likes of Conn Smythe who thought the opposite. That it would be a great sales tool for the game. By about 1953/54 sales of television sets in Toronto & Montreal were hitting numbers as high as 50,000 per month as people clamored to keep up with the changing technologies. Hockey Night in Canada initially aired late, from the 2nd period on as there were still some concerns that TV would affect the gate & ticket sales. Whats really quite incredible is that by 1955 when audience stats starting to be counted, a whopping 77% of all TV sets in Montreal were tuned to Hockey Night in Canada when games were played at the Forum.... not sure what they were in Toronto but Id hazard to guess not a lot lower.