Easier, yes…but not necessary. Anyone remember a Zorro film from about 10 years back with Anthony Hopkins as retired Zorro and Antonio Banderas as new Zorro? It did well enough they made a sequel.
Other characters have legacy built into the concept, like the Phantom (maybe not the best example, because the movie tanked).
Maybe a better example: a big part of the first Pirates of the Caribbean film hinged on Will Turner following through on his father’s legacy, but Bootstrap Bill didn’t appear at all until they did the sequels.
Or, heck, Harry Potter – it’s all about this boy growing up and living up to the legacy of his parents and their generation who fought in a war. Harry’s parents are absolutely critical to his story, but they’ve been dead for 10 years when the first movie gets going.
So yes, a legacy character *can* be done in a movie. It may be *easier* to tell a story about the first guy, but it’s not *necessary.*