An overdone series is simply one in which the creators chose to keep giving us game after game following the same basic theme or plot.
Actually, a better way to define the term is by listing some of the series that I feel have been overdone.
Pokemon (I almost threw up typing that word - so darn many Pokemon games have been made, all following the same style.)
The Mario games (I've made a joke about Nintendo eventually releasing Super Mario 97 - you play as an older Mario with a cane; half the game is saving Peach and defeating Bowser, the other half is making sure Mario remembers who to save and who to defeat.)
The Sims (I know there are only five Sims games I consider canon - The Sims, The Sims 2, The Sims Bustin' Out, The Sims 3, and The Sims 4 - none of the MySims games belong in the same line) After playing one for about ten minutes, you know precisely what to expect in all future Sims games.
I know there are plenty of other candidates: Mortal Kombat, Dragon Warrior, Final Fantasy, and Mega Man just to name a few.
I'd also like to avoid bashing any of these series (except Pokemon, maybe.)
Interested in Animal Crossing: New Horizons trading? PM me!