I've never felt any desire to re-visit Iron Man 3, Thor 2 or The Incredible Hulk. So I'm going to go with one of them.

Objectively speaking, I'd say that almost all of the Marvel movies are just honest (though usually pretty amusing) pop movies, without any pretence of being great art. They're all made from the same recipe, and it's pretty hard to say that one was truly bad when compared to the others. Of course, some were more entertaining, or done with more skill, but I think that the fairest metric to use here is the one Slam brought up: which ones don't we feel like watching again?

In my case, without any judgement, here are the ones I saw only once and don't feel like seeing again:

Captain America: the First Avenger
Ant-Man and the Wasp
Captain Marvel
Iron Man 2
Guardians of the galaxy vol. 2
*edit*
Shang-Chi, too.

I did watch Age of Ultron again, but won't do it a third time.

I hasten to add that I didn't dislike any of these movies; they just weren't special enough for me to want to revisit them.

Iron Man 3 was pretty good, I thought, including its twist about the Mandarin not being an actual super-villain; what killed it for me was the overlong and epilepsy-inducing CGI battle at the end. I want to watch a movie, not a videogame.

And Thor: the Dark World remains one of my favourites. Not only in terms of enjoyment, but in the way it managed to give all of the supporting cast a moment to shine. It's also the movie that turned Loki from a funny villain with good lines into an actual character; Hiddleston's reaction to the death of his mother was a rare moment of Thespian grace in this multibillion dollars franchise.

That could likely be added in to my list.  I honestly only vaguely remember it, mostly for Kurt Russell.  

Incredible Hulk, mostly due to the bad CGI on Hulk and, especially, Abomination.

Cei-U!
I summon the eyesore!

I haven't seen Shang-Chi or Black Widow; so, they get a pass. Both Iron Man sequels do little for me and the second was a complete waste of Justin Hammer and Whiplash. They were in a position to do an adaptation of Demon in a Bottle, which is something Downey could have sunk his teeth into, but went with blah stories. Captain Marvel didn't do much for me at all; not bad, just not interesting and they added nothing to the character and didn't particularly use Carol Danvers well or reference Mar-Vell's history well. The Skrulls were about the high point, such as there was one.

Thor 2 was completely forgettable and 1 suffered from having a truncated third act to feed into Avengers.

Avengers 1 and 2 are fine while watching but devoid of any real meat for my brain. The Thanos stuff was much better.

Incredible Hulk is okay, but nothing spectacular and they really seem to have little imagination for the character. I liked him far more in Thor: Ragnarok and the later Avengers.

I like the Ant-Man films; nice caper stuff, not too heavy, not completely jokey. GOTG is fun for what it is, which is mindless Star Wars stuff, with better dialogue and my childhood for a soundtrack. 2 was weaker, but enjoyable enough.

Of what I have seen, I'd put Captain Marvel, Iron Man 2 & 3, and Thor 2 at the bottom of the list, in no particular order. Each has bits here and there; but, are underwhelming, for my tastes. To me, they are much like the average Marvel story where they are just keeping the book going, before someone imaginative took over.

Really, the formulaic stories were worn thin after Phase 1. Captain America has been the one really consistent sub-franchise, thanks to both Chris Evans and people like the Russo Brothers. It just seems to bring out something in those involved. Hemsworth is good in the Thor films, but the early efforts can get ponderous and Hiddleston steals the films. Ragnarok gave it a nice fun jolt, rather like what Walt Simonson did, in the comics, for me. Avengers just seemed like generic fights with a thin plot to link fight scenes and a bunch of one liners, until Infinity War/Endgame. Guardians was fun, if rather mindless and often sophomoric. Sometimes dumb works.

Ant-Man gets a lot of mileage out of the actors and the personality they give the characters helps elevate the material, plus, I enjoy caper films. These aren't Topkapi or even Who's Minding the Mint?; but, they get enough right, for me.

I liked Black Panther and loved the Agent Carter series and would have loved a whole Peggy carter film series, across the decades.

I think it is time for Marvel Studios to step up and start working beyond the formulaic superhero properties and explore their other characters and genres (DC, too). I'd like to see them do a western franchise and maybe the Howling Commandos, without Cap, or Dominic Fortune, Killraven, Deathlok, or some of their horror characters. Tomb of Dracula should be a no-brainer.

We are supposedly getting a Blade TV series, which could be a sort of ToD series, depending on how they do it, but it wouldn't focus on Dracula obviously.

That said, I don't think they'll actually introduce Dracula into the MCU. There would have to be a lot of explanation about how he exists there, so they'd likely just create another "Big Bad" vampire to serve that role.