Despite the mediocrity of the Garfield comic strip, I think a lot of Garfield's enduring popularity among late Gen X / early Millennials can be attributed to the late 80s Garfield and Friends cartoon [1]. It was actually funny, largely due to the writing by Mark Evanier. He's also known for his snappy dialogue on Groo the Wanderer, among other comic books.
And then in the late 00s, Garfield got an indie-cred boost from Garfield Minus Garfield [2], the surreal and often humorously bleak webcomic.
Groo was always a favorite of mine as a child. The amazing art of Sergio Aragones and the sarcasm and double speak that pervade the comic always connected better with me. That came across in the Aragones panels in Mad much of the time as well.
Same! They actually still put out new issues, in the form of a new 4-issue mini series roughly once per year. It's the only comic book I regularly read as an adult. Pretty amazing that Sergio is still doing this at age 88!