Some context from the linked Puck Daddy post
This is up 46% from the 2002 USA/Canada showdown, and will very likely be the highest-rated hockey game since 1980. The share means that 1 in every 3 Americans with a TV were watching the game. This is, to put it professionally, out of this world.
Sunday's game drew a higher overnight rating than every World Series game since 2004 (including every game of Yankees/Phillies last year), every NBA Finals telecast since 1998, and every NCAA Men's Basketball Final Four game since at least '98. Excluding the NFL, the 17.6 overnight for the game is the second-highest of the year for any sporting event, behind only the Texas/Alabama BCS National Championship Game in January (18.2).