Okay so I just completed Playoff Mode on Wayne Gretzky's 3D Hockey '98 with the Toronto Maple Leafs.
Definitely took longer than I expected, but it was still pretty fun. I can't say if its a 'good' hockey game for the N64 however since this is the only one I have ever played on the console.
I would estimate around 4 hours to beat the whole mode over about 3 days.
I am very much enjoying FINALLY delving into NFL Blitz. My Broncos are 3-0 (well, after a few restarts and non-saves). Fun game; I would have not pierced the surface of outside of our collective quest.