I think 1972 probably wins simply because of the circumstances. It was the first best on best contest between hockey's two top nations, which happened to come while the Cold War was still extremely frosty. There was a true sense of us vs them. That the soviets were rather unknown, and that Canada travelled "behind enemy lines" to Moscow I think added to the mystique as well.
Also, This wasn't just a winner takes all, anything can happen game, but rather a gruelling 8 game series. I don't think that can be stressed more. The two best hockey playing nations (at the time) went at each other for 8 whole games. There were no warm-ups, no round-robin games, and no matches vs. the likes of Norway, or France, Italy.
Second for me though has to be 1998. Hockey in Canada was at a real low in the late 90's. Former greats like Gretzky and Messier were shadows of their former selves, Lemieux was unable to suit-up for the national team (illness, injury, retirement), and the nation as a whole was suffering (as hockey fans). Quebec and Winnipeg had already succumbed to the economic realities of the 90's NHL and it looked as though Calgary, Ottawa, and very nearly Edmonton (only a last-minute ownership consortium saved them) were next. Adding insult to injury, the USA led by an MVP performance from Richter beat us at our own game in Montreal, walking away with the inaugural World Cup.
For this reason, and of course the fact that NHLers were taking a mid-season break for the first time at the Olympic Games, the pressure was really on the boys in 1998. This was supposed to be the chance for Canada's new generation (you don't think it was significant that Lindros was named Captain?) to regain hockey glory. Losing to the czechs in the shootout was absolutely devastating.
Anyone who follows Team Canada and knows about the history of "Best on Best" tournaments knows that the answer to this is easilly 1998
The thing people forget about 1972 is there wasn't any pressure on Team Canada going into Game 1. Everyone thought they would win the series 8-0. Yes as the tournament went on the pressure mounted, but would everyone look at it the same had the Soviets Won? It's doubtful.
After Canada lost the '96 World Cup, the pressure to win in Nagano, in the 1st "professional" Olympics is unmatched. When Canada lost, it sent the country into mourning. The same cannot be said for 2006, or if we fail in 2014. That tournament was one of the kind, especially when you consider the legends on that team and how it would have added to their resumes had we won.
I am not Canadian, so didnt live through these first hand. What I mean by that is reading about it in the papers everyday, seeing it on the news and so forth. However, based on the situation, I would think in this order:
1984: Getting blown out in the 81 final, Tretiak had retired. This team had to win it all.
1998: 18 months after losing the World Cup by losing 2 straight in Canada. First time NHLers were playing. Heavy favorites.
2010: In Canada, terrible showing in 2006. Rough start by losing to the US in the prelims, switching goalies.
2002: Had been 50 years since they won Gold (I know Canada didn't send a team for a while to protest the Soviets using their pros).
1972: I put them down here only because I don't think the pressure started until after they dropped 2 games in Canada. As the OP said, it was supposed to be a cakewalk, but that was only because they under-estimated the Soviets. They beat up on the US and Canadian amateurs, but showed they were just as good. I have watched all 8 games, I have read a lot about that series. I think the slow start was just a case of the players and coaches not respecting the Soviets. I remember watching a special on the 80 Olympics and Tretiak said of the Americans, "We didn't respect them....and you can't do that in hockey." I think the 72 Canada team had the same problem.