The performance wasn't very close. 2015 had GF 39 GA 6 in seven games compared to 2005 GF 42 GA 7 in six games, with the most significant difference being that Canada 2015 had to play Denmark in the quarterfinals, while Canada 2005 had a bye right to the semi finals. The 2005 team never came remotely close to losing and destroyed Russia featuring a 19 year old Ovechkin and an 18 year old Malkin, while we all saw what 2015 Canada did against a standard Russian team. There's no comparison statistically or otherwise.
Add all of the players and plenty of years look like they could potentially challenge 2005, but who knows. 2010 could have had something like Stamkos, Tavares, Duchene, Kane, O'Reilly, Myers, Del Zotto, Hodgson all added to it if they were not in the NHL and healthy, but we don't know.
People forget that the 2005 team was missing players as well. I believe Nathan Horton (recent #3 overall pick with a solid rookie year in the NHL) was injured, and Minnesota wouldn't release Brent Burns. That team could have been better too.