In Your Opinion are The Russo's now The greatest CBM's Directors of all time?

Yes. They are but not because of Endgame. Endgame was a solid conclusion but Winter Solder and Infinity War are the giants of the MCU. I have Endgame tied for third with Guardians of the Galaxy and Civil War(Russos again).

Endgame did not disappoint as it had all the elements to be up there with Infinity War and Winter Soldier but it really needed to spend more time on the time heist. It rushed through it too quickly when thats supposed to be the movie's hook.

While comparing directors, the criteria should be more based on what unique voice and execution that the directors have brought to the table compared to the previous movies of the genre. I believe the MCU is largely a producer driven vision rather than the individual directors. I'll probably rate Nolan, Sam raimi, Bryan Singer, Richard Donner, Tim Burton as better directors than Russo's even though I like MCU movies more than most of the above director's filmography.

You should add Donner to that list. Superman I and II were by far the best comicbook movies untill Batman came out.

The Russos were already number one before Endgame was released.

1. Russos
2. Whedon
3. Singer
4. Raimi
5. Donner

I don't consider The Dark Knight movies to be comicbook movies. They are Nolan movies. That's why he doesn't make this list.

I definitely think that Joe and Anthony Russo deserve to be considered the best CBM directors of all time.

It's a tough one. Sam Rami made some fantastic Spider-man movies but he's a director with a myriad of interests and I think he still prefers the horror genre. Christopher Nolan made the absolutely best Batman movies, yet he's stated that he's pretty much done with superheros. So when you consider that the Russo's are both big comicbook guys, I think you have to give them the nod. They did make four of the best damn MCU movies - Winter Soldier, Civil War (personal favorite), Infinity War and Endgame. Those are all great entries and since they're towards the end of a movie saga that spans all the way back to the first Avengers movie and the intro of Thanos, I think that accomplishment speaks volumes.

They are definitely in the top 10, and an improvement over Joss Whedon as the directors of Avengers movies

One thing I will say, though, is I disagree with their choice to make Thanos a "sympathetic" villain in Infinity War

I may be in the minority, but I DON'T feel like he was one of the greatest villains of all time, at least from a writing standpoint. They tried to make him seem intelligent and like he "had a point", but his plan was stupid as fuck. I found his character to be extremely corny in Infinity War, especially the way he was acting like a sadboi over Gamora's death, but there had been very little in the previous movies to get us invested in their relationship. And now they expect those scenes between him and Gamora to resonate and carry emotional weight?

I think Civil War and Infinity War were very flawed films. Endgame was much better, IMO. Winter Soldier is obviously the best. You can't really blame the Russos for being given the responsibility of bringing such complicated stories to life, but I feel like 2/4 of their movies were kind of "meh"