When Jack Kirby returned to Marvel, of course they had him draw some Fantastic Four covers. Here are two favorites...
Fantastic Four #176 featured one of the best stories executed by Roy Thomas and George Perez. The Impossible Man ran amok in New York City, tearing up the Marvel Bullpen and demanding to have his own comic. All the bullpeners of the day make an appearance, including Stan and Jack. The cover captures this crazy frenetic action of the Impossible Man perfectly.
Marvel Treasury Edition #11 featured a compendium of reprints, with this cover of Doc Doom looming over the FF. This reminds me of the John Byrne story, Terror in a Tiny Town, but I don't think there's any relationship between the two.
Fabulous Fantastic Four? Too many adjectives in that logo. Nuff Said!