The Flintstones - timeless classic, yes I know it's so damn old my parents loved it when they were kids.
Bugs & Tweety - same as above.
Astroboy
Teenage Mutant Ninja Turtles - if you were born and raised in the 80s, this must be on your list.
Garfield & Friends
Goof Troop - to this day still one of the funniest kid cartoons ever.
Chip & Dale Rescue Rangers (theme song just popped into my head. Ch-Ch-Ch-CHIP & DALE... Rescue Rangers...)
DuckTales
Johnny Quest
Batman the Animated Series
Animaniacs/Pinky and the Brain
X-Men
Spider-Man (from mid-90s)
X-Men Evolution was alright at first and then I kind of fell out of it after while