Director Joe Russo made it clear at last year's Comic-Con International in San Diego that he wants Avengers: Infinity War's Thanos to be the "Darth Vader for a new generation," a sentiment that he recently reiterated. In both statements, Russo emphasized -- among other things -- the power, cruelty and complexity of the Mad Titan, traits that he also attributed to Star Wars' most iconic villain.
However, Vader is so much more than those adjectival descriptions. That's why, regardless of how great he may prove to be in Infinity War and Avengers 4, Thanos won't be able to recreate the factors that have helped the Dark Lord of the Sith appeal to so many generations since his first appearance in 1977.
Even before Infinity War arrives, Thanos' relationship to audience expectations is fundamentally different from Darth Vader because of the hype that Marvel has built around the Mad Titan. There are also storytelling purposes that Vader serves in Star Wars that helped solidify his legacy in a way that Thanos simply cannot at this point.
Vader's Motivations Aren't Always Clear
The first place to start is their goals, as it's one of the key things that shapes how they interact with their respective film worlds. While the specifics aren't yet clear, it's safe to assume that Thanos' ultimate goals won't differ much from those of his comic book counterpart: Power and destruction. Thanos wants to use the Infinity Stones and Gauntlet to achieve those aims. He is a fundamentally simple character.
Vader's goals are much more more complex, because they involve his own role in the life of another human being. When he first appears at the start of A New Hope, Vader is something uncanny, a mixture of robotics and humanity, which serves as an immediate signifier that he's something to be feared. His goal, however, is simple and easily understood: Crush the Rebel Alliance. However, his aims change drastically in The Empire Strikes Back, when he starts attempting to turn his son to the Dark Side. By the end, the Star Wars films have unveiled a history and humanity to the fearsome, awe-inspiring character without ever undermining his power. Vader is an infinitely complex figure, and that's important to his enduring appeal; it's why Lucasfilm made three films centered on him prior to his fall.
The MCU Has Spent 6 Years Building Up Thanos
There's little mystery surrounding how powerful Thanos is going into Infinity War, and it's likely he'll kill an Avenger or two before achieving his ultimate goal. Marvel Studios President Kevin Feige has made it clear that "within the first five minutes of Infinity War, people will understand why Thanos is the biggest and baddest villain in the history of the Marvel Cinematic Universe." Thanos will clearly be showing his power from the start of the film, which is much different than Vader.
There are fewer expectations regarding Vader's strength at the start of the original trilogy, allowing him to become more terrifying with each new power and ability that the audience sees. Vader's skills, especially in his usage of the Force, are revealed slowly as he uses them to brutality murder others. By the time The Empire Strikes Back ends, director George Lucas has established Vader as a nigh-invincible monster, having him kill Obi-Wan, stop a blaster shot from Han Solo with a wave of his hand. and easily dispatch Luke Skywalker in a lightsaber duel. Each time he appears on screen, Vader demonstrates that he's even more powerful than he previously seemed.
The difference here between Thanos and Vader is, while Thanos must live up to the expectations that previous films and the MCU have set up for him, Vader inspires awe because of his ability to show how powerful he is gradually. Luke and the audience learn Vader's power together, making the Sith Lord appear larger than life.