I'm not really familiar enough with a lot of directors to say much on this, but I'd definitely agree with Iwao Takamoto, since he worked on Scooby-Doo!
(and lots of other Hanna-Barbera shows, I'm sure.)
Other than that, I would mention Ralph Bakshi, since he did some great animated movies as well (animated "Lord of the Rings" movies particularly and Marvel's '60s "Spider-Man" cartoon. And he's known for the 1977 "Wizards" animated movie.) The biggest '80s production he had for my interests, would have to be "The New Adventures of Mighty Mouse" cartoon.
Another favorite would be Don Bluth, well known for "The Secret of Nimh" in 1982. Other '80s favorites include both "Dragon's Lair" and "Space Ace" (the video games)- and three of my favorite '80s animated movies- "The Land Before Time", "All Dogs Go to Heaven" and "An American Tail". (LOVE that movie! I remember seeing it in theaters as a kid- such a great, sweet and funny movie.)
He also continued to belt out a number of hits in the 1990s- "Rock-A-Doodle", "Thumbelina", "A Troll in Central Park", "The Pebble and the Penguin", "Anastasia", "Titan A.E."- lots of great stuff.
And one other favorite for me that I have to mention is a Disney short he directed in 1978- "The Small One". This is a very sweet Disney animated Christmas short that depicts the birth of Jesus Christ. It is respectfully well done and foreshadows in some ways the meaning of Christ's coming and the sacrifice He would give at Calvary when He died and rose for all our sins.
It's nice to see a Disney production acknowledge the reason Christians celebrate Christmas and what it's really all about- so that is definitely a particularly poignant favorite for me.
That's probably honestly about all the big cartoon directors I can think of right now.
If we were talking about any time period, I would mention Chuck Jones for Looney Tunes cartoons and Tex Avery- but those are animation legends for another thread.
"I am the Way, the Truth, and the Life. No man comes to the Father but by me." - Jesus (John 14:6)
"You can do anything you want to do if you put your mind to it."- MacGyver