One great 'DC Star Wars Crossover Fanfiction' is 'The Jedi of Gotham'. It combines the dark and brooding atmosphere of Gotham with the Force - using elements of both universes really well. Another one is 'Superman in the Galaxy Far, Far Away' which has Superman dealing with the politics and battles in the Star Wars universe in an interesting way.
One idea could be having Batman meet Darth Vader. Batman, with his detective skills, might try to figure out Vader's true identity behind the mask. Another could be Wonder Woman and Leia teaming up. They are both strong female leaders, and together they could lead a combined force against a common enemy. Or perhaps Superman and Luke Skywalker could have a power - sharing adventure, learning from each other's unique abilities.
It's really hard to say. Superman has incredible strength, speed, and a whole bunch of other powers. But then you have characters like Darth Sidious who are extremely powerful in the Force. If they were to face off, it would depend on the situation. Maybe in a physical fight, Superman would have the upper hand, but Sidious could use the Force to manipulate and deceive. So it could go either way.
First, they need to understand the core elements of both universes. For DC, it's the heroes and their unique powers and personalities. In Star Wars, it's the Force, the different species, and the political landscape. Then, they can start by creating a believable way for the two universes to collide, like a portal or some kind of interdimensional rift.
Starkiller can be a game - changer in Star Wars crossover fanfiction. He can bring his combat skills and Force knowledge to new settings. For example, if he's in a crossover with the Matrix universe, his ability to sense and manipulate the Force could be compared to Neo's ability to control the Matrix.
One possible fanfiction could be about a Sith Lord from Star Wars ending up in the Naruto universe. Maybe he tries to use the Force to control the chakra, but finds that it's a completely different power system. He could then form an alliance with some of the villains in Naruto, like Orochimaru, who are also interested in power and dark arts.
The cultures in both universes are also ripe for exploration in the crossover. The Federation's values of equality and cooperation in Star Trek contrast with the more hierarchical and often morally ambiguous cultures in Star Wars. A story could focus on how characters from each side learn from or clash with the other's cultural norms.
Star Wars could be more popular in fanfiction. The Star Wars universe is so unique with its blend of science - fiction and fantasy elements. Fans are often drawn to writing about the Force, the Jedi, and the Sith. There are countless possibilities for stories set in different eras of the Star Wars timeline, from the Old Republic to the sequel trilogy. In contrast, while Marvel/DC have their own great concepts, the Star Wars lore offers a more distinct and immersive world for fanfiction writers to play in.
The fanfiction 'Rey Meets the Avengers' is also a good one. In this story, Rey teams up with the Avengers. Her lightsaber skills are a huge asset when facing off against the villains. She has some really cool interactions with Iron Man, as they both are sort of tech - savvy in their own ways.
A great idea for an Echo x Star Wars Rebels crossover fanfiction would be that Echo has some sort of encrypted data in his cybernetic enhancements that could be crucial for the Rebels. The Rebels have to figure out a way to access it without harming Echo. This could lead to a lot of character - development moments as they get to know Echo and his past better, and Echo gets to adapt to the Rebels' way of doing things.