I have a pretty bad case of Vinnyitus for most forms of media. If someone tells me that a sequel is good unless it has absolutely no canon ties to prior entries (like most of the Final Fantasy series) I generally will want to play/watch/read those before getting to the sequel. There are some exceptions for genres that absolutely don't rely on story or established characters (like most fighting game series) but story driven stuff it's a must.
Sometimes this works out okay. I played all of the major prior God of War games before playing the 2018 entry, and while I think that was totally unnecessary considering how thin the ties are, those games ranged from mediocre but not bad (the PSP games) to pretty darned good (God of War III.) I even played Dante's Inferno as part of the experience just to see what the God of War clones were like at the time. That game's not quite as bad as people say, though it's hardly a must play.
I had a lot of fun going through the Halo and Gears series with a friend towards the beginning of the Xbox One era after those games were made available (in the MCC and through back compat), both of us talking about how the series evolved over time and just having fun playing them co-op together.
Sometimes this works out less well. I love Ratchet and Clank but I really did not need to play Full Frontal Assault or All 4 One. They aren't horrible games but they really aren't worth going back to. There I did not play the PSP titles because I would have had to do so on my Vita and I really do not like handheld gaming. If they are released for the new PS+ service to play on PS4/5 I will almost certainly play them.
Uncharted: Golden Abyss is another game that wasn't terrible but I really could have skipped. I played that a year ago and I have almost no memory of it beyond the basic outlines of its pretty boring plot.
So I'd like to hear about your worst Vinnyitus experiences and if there has ever been a game so bad that it stopped you from getting to the later games in a series. That has definitely happened to me, in Rayman of all things (which I know is not very story based, at least for the first game.) I wouldn't say the first Rayman game is bad but it is very difficult and I just got frustrated and gave up, so I never played the later Rayman 3D Platformers or even Legends and Origin, all of which I own and all of which I would probably enjoy much more than the first. Similarly I have all the Gex games on my PS3 and I'd probably like the 3D platformers but I found Gex 1 to be a boring chore.
I know I'm not alone in this, so spill your secrets!
ETA: Oh I forgot the biggest one for me! The Witcher. Pretty much everyone agrees the first Witcher game is hard to go back to so I've never played the series OR watched the TV show because I'd have to force myself to slog through that first. Some day maybe.