What he meant was: "I just finished the main story line."
What he hasn't finished:
Special Ops mode (twenty three one-shot missions with special objectives. Award for beating all of them on Veteran 3-star rating) (and co-op too)
Multiplayer challenges (holy **** are there a lot of these). They also net you weapon upgrades and perks for multi games.
which goes into: Prestige mode. Max out your rank? Oh well! Click on the prestige button to get a cool new rank insignia and start over at one again! (TEN TIMES!). Max rank is 75 I think for this game. Oh, Prestige Mode resets all multi challenges as well (not achievments, just challenges). I think this time you get something more than a pretty new rank symbol though.
Now let's look at Zelda.
Single player. That's it. A dedicated player could finish the two probably in the same amount of time.
And CoD isn't a puzzle game, even in the slightest, so you could chuck a few hours of Zelda out the window if we're just looking at story and gameplay. And a few more for having to restart that damn three headed turtle boss three dozen times anyway. And a dozen more for finding all the heart pieces.
If anything, modern console games have even more replayability and longevity compared to back in the day games, thanks to the advent of online multiplayer.