There are plenty of series that undid what I liked about the previous entries or otherwise overstayed there welcome.
-Skyrim: Morrowind is my favorite game in the series by a longshot. Skyrim Blew up Vvardenfell and had mainland Morrowind overrun by the friggin Argonians. Why they would want to completely wipe clean their most iconic locale is something I will never get. But I would like to think that my actions in ES III were in some way meaningful and had some sort of role in preserving said culture/environment I enjoyed so much. But Skyrim slammed the door on that hard. Nevermind my quibbles on the new mechanics, the story etc.
-Breath of Fire: If BoF 4 had been the last, the series would have ended on a good note, and wouldn't have dropped into a coma after the abject failure of V until being rebooted as an insulting social phone game with awful art.
-The Old Republic: Many of the same problems I have with where Elder Scrolls went. The main characters from the first two games are handled in an awful manner-canon alignments and gender, one killed off in a backhanded ,mannerin between games, the other stuffed in a fridge...*not actually being able to play as either*...but worst for me is turning a single player RPG into a FTP MMO. Couldn't be more blatant a cash-in if it tried.
-Neverwinter: *Stop making my favorite RPG series into MMOs!*
-Master of Orion 3: *eye twitch* MoO 2 should have been the last.
-Total War: The series has gotten progressively more arcade-y with infantry that run like olympic sprinters, cooldown powers (fire arrows in Shogun 2 come to mind) DLC units, DLC factions...DLC in general. Purposefully making the game less moddable. etc. The series just isn't what it used to be.
-Dragon Age: I think it should have ended with the first game. The game never really had a terribly original setting or aesthetic-mostly being cobbled together from half a dozen other IPs I would have rather had an RPG of...but the first game was quite well executed and surprised me with the quality. Since then, Bioware has squandered the goodwill they got out of me with that. Constant retcons, complete turnabouts on gameplay focus, aesthetics. and wildly inconsistent application of effects of the player's actions make following this franchise a serious case of whiplash.
Medievil: I have no idea what they were thinking with Medievil 2 and Resurrection, but the series was best when it stuck to the dark humor and well designed levels and mechanics. The sequels did away with these and were much more 'wacky' and had soem really frustrating level design and gimmicks. Probably for the better the series died off.