A large part of what makes albums classics are the context of their time period. We have no idea about how the album will be recognized years from now, but GKMC does have many of the traits of a classic album. Mainly, critical acclaim/huge accolades when it came out, sales (if I'm not mistaken, the only rap record to sell more than GKMC in 2012 was Nicki Minaj's album - that says a lot), and the foundation for him to become a star after it dropped. Plus, I think the influence of the album is already taking its toll, because many albums that have dropped since then that likely would have been critically praised - Dreams & Nightmares and MCHG, for example - have sort of came and went because fans are expecting more.
I do admit that it didn't have individual songs that were as BIG as some classic albums; ie, doesn't have a Protect Ya Neck or a Juicy. But the album still has made much of the impact that a classic consists of. Plus, as a rapper, Kendrick is well-rounded. Punchlines/wordplay are probably the only weaknesses in his repertoire. He has shyt-talking songs, he has storytelling songs, he can hop on commercial songs and fit in well, his flow is on point, his imagery is strong. Honestly, punchlines aren't even a necessary skill for him. That's like saying Peyton Manning is weak because he isn't a good blocker.
It amazes me that people on here try to say he isn't shyt - like GKMC didn't have one of the strongest full-length narratives on a rap album in years, like he isn't able to insert fully-developed characters in his music, like he isn't able to cover various topics with incredible depth. Just about everyone who blows up big way in hip-hop has a big push behind them in one way or another. But people who aren't talented get huge pushes, too. The defining factor usually talent when it comes to who sticks around. Hasn't been a long time yet, but with Section.80 and GKMC, IMO, Kendrick is showing that he'll stick around. It really feels like people who hate on him at this point are being contrarian; I wonder if they were saying those things when GKMC actually dropped.
I think a better comparison is LeBron James, before he won his first championship. He's definitely putting up MVP numbers, even if he hasn't gotten a ring yet.