I don't necessarily disagree with either of these, but I have to chuckle at how they're held up in retrospect (not just by the people listing them in this thread, but by many many fans and posters on these forums), because fans of Thornton and Ovechkin (until last year) would shout until they were blue in the face that the reason those stars hadn't won the big one yet (Stanley Cup) was a lack of support relative to their more accomplished peers. But it's crazy to argue both a) they were part of one of the best teams in the league in any given year and b) they had no supporting cast simultaneously. The Sharks in particular, were a popular pick to make the Finals or win the cup for like a five year span.... yet Thornton never won because his teams sucked? It was always lunacy to me.
Anyway, my picks:
2009 Red Wings - On paper, they were a better team than the 2008 Red Wings that just murdered the league and remain the best cap-era team to this day. But injuries down the stretch prevented them from reaching the ultimate goal. And thank god for that, cause my team got Hossa as a result.
2011 Canucks - I don't think they were as good as some Canucks fans claim them to be, but there's no doubt they were the best team in the league that year. They just ran into injuries and a historical goaltending performance. Bad luck.
2014 Blackhawks - They took a step back in terms of their forward depth after turning the league to mulch in 2013, but they were still a crazy dominant team getting career years out of all their major talent. They went up against the only team in the league on their level, went to 7 games, and ultimately some bad coaching decisions that took far too long to address sewed their undoing. Ah well. Winning the cup in 2015 helped sooth the wound.
2015 Lighting - Speaking of which, the Blackhawks probably shouldn't have won the cup in 2015. That's not to say they weren't even in the conversation. They were just the second best team in the league all year... until the SCF. Injuries to who was essentially Tampa's 1C at the time (Johnson), as well as their number 1 goalie, and the fact that Stamkos picked a bad time to get snake-bit, all worked against them.
2016 Capitals - I mean, what can you say? I was honestly dumbfounded watching that 2nd round series.