Of all the films in the past decade, I feel like this is the most under-appreciated of them. It doesn't come as much of a surprise, as Firefly is one of the most ignored classic television shows in existence. It was one of the shows I was most saddened to see canceled, right along with Pushing Daisies, which still hasn't been adapted into a feature length film. Serenity was kind of a continuation of Firefly, and in some ways, a conclusion of the series. I was concerned that it might be difficult for audiences to jump into and enjoy, but it really isn't. It's not a film strictly made for fans of the original series. It's a fantastic sci-fi action-adventure with a dark edge that it doesn't care to hide.
In terms of history, I don't think this is going to go down as one of the best films of the past century, but it's certainly one of the most enjoyable. Nathan Fillion's character is pretty much the inspiration for the a-hole hero type of character that Tony Stark turned into in the Iron Man films, and pretty much every character like him. You can even see shades of him in Flynn Rider from Tangled. Fillion adds much to the film, and the script is actually kind of smart and funny and a bit tragic to tell the truth. The visual effects aren't the best, but they're spectacular for the budget they've been afforded. Ultimately, Serenity's the sort of film that I kind of miss and wish they made more of.