STAR WARS SPOILERS AHEAD, SKIP IF NOT WACHED YET.
Below: my long commentary of The Force Awakens.
I loved The Force Awakens, despite the fact that the plot scores pretty low in originality. It's not a normal sequel, it's a remake/reboot of sorts: a more honest title would be Empire Strikes Back Again. Themes from the original trilogy are copied so often, and so blatantly, it's obviously purposeful and not just a poor job of screenwriting.
And I for one, am perfectly fine with that! Look, A New Hope will be 40 years old soon. I call Star Wars a story "from my time", but the first movie I actually watched in the theater was ROTJ, I was too young when the others were released. I recently watched the whole trilogy again and enjoyed it massively; can repeat that experience every 5 years forever and it's always the same thrill. (I also re-watched all 3 prequels again, but for the first time since their release... TPM still sucks, they other two are actually OK, better than my memories, but still a step below any of the original trilogy.) Keeping a franchise like this alive for so long is very difficult, and the need for a fresh start is necessary at some point. Now, the classic way to get that fresh start is with a conventional reboot – filming the same story again, or at least the same characters and general setting. But that works well for old movies that didn't age well or were mostly forgotten; not so much for classics that were executed amazingly, stood very well to the passing of time, and are still loved by millions.
The Force Awakens is a smarter kind of reboot. The story starts decades after the end of ROTJ. The defeat of the Empire in the end of ROTJ was not complete; it retreats but later regroups and grows, with another name but very similar form, including leadership of a super-villain who masters the Dark Side. And everything old is new again, the rest of the story is mostly a big patchwork of the original trilogy... here we go again with Jedi dinasties, disciples turning dark, the Millenium Falcon running on bubblegum and duct tape, Death Star III destroying planets until an easy weak point is exploited, Han Solo running from his customers, and on and on. Even an exquisite alien bar is there.
(*) At least to my surprise, not having read/watched anything other than Episodes I-VI.
Several characters, actors, and even ships and robots from the classic trilogy make significant cameos, remarkably Han Solo; and that's awesome, but it's also great that he dies in the end. I'm OK with the appeal to the old guard, but we also need to say goodbye, allowing new heroes to grow. Luke will be the obvious exception: this entire movie was a big teaser for Mark Hamill's character – and only delivers more teasing in the end, with promise of a much bigger role in the next movie (New Return of the Jedi?...). But in that case I'll be happy to extend the veteran's cameo; Star Wars always needs the "old Jedi master" role, and Luke will be perfect to replace Obi-Wan and Yoda. Mark's now the perfect age for this, old enough to be the legendary wise master / tutor but young enough for some lightsaber-kicking. And we already love Mark! He will have none of the difficulty other "new" actors / characters had in the prequels, to win the hearts of the Star War fans.
All that said, TFA also brings important innovations. I love the main hero now being a woman, not just for modernity's sake but just as one important and interesting change to keep Star Wars fresh. I love having a Storm Trooper defector joining the good guys, which never happened before: it was always good people falling to the dark side, depressing!! and too much standard morality from classic myths/religions (one starts good, is tempted by evil and falls for it; after inner struggle repents, but can only get salvation through sacrifice). Finn is a very welcome alternative to that: one is conditioned to evil by his environment, but finds the strength to escape that fate, no need for expiation. (Too bad he didn't actually commit any important evil act before desertion; but hey, it's still a Disney movie so I'll take what I can get.)
Kylo Ren is fifty-fifty between a Darth Vader rehash and new ideas. He's infinitely more interesting as a character than the zero-dimensional Darth Maul. The way he reveals his face early, instead of hiding behind the mask for an entire trilogy, is a very nice touch already. The climactic resolution of his struggle to embrace the dark side is really great, even if predictable (hey, it's not like the original trilogy was some Agatha Christie story with real surprises...). I'm less sure I like his ending (for now): defeated and badly wounded but not killed, will be "fixed" by evil boss with artificial parts next time we see him. But this repetition of story makes sense since Ren had the obsession to become a heir of his grandpa, so what better way to do that than going through the same ordeal. That's another common mythological theme, the Faustian bargain for power that requires sacrificing both soul and body. I only hope the repetition ends here and the next movies evolve the character in novel ways; for one thing, at least he isn't Rey's dad. For one thing, it would be great if Ren succeeds where Vader failed, dethroning the Supreme Leader quickly instead of playing his minion for an entire trilogy. Indeed, this can be a great main plot for the next movie: Snoke turns him in a Vader-like cyborg, and completes his training like announced; but then Ren grows stronger than anticipated, betrays his master and kills him in the great climax of the episode; in the next part he starts as the top ruler, evolving the First Order into a fully-restored Galactic Empire. (I'm happy to provide a full plot, after Disney sends a big check.)
Speaking of Rey again, she starts pretty much like Luke (and Anakin...) but becomes her own role quicker. I'd even say, already a more original character than Luke Skywalker (because, really, Luke is just a perfect Hero's Journey stereotype with virtually no new ideas -- the single exception is the tragedy of being the villain's son). Her involvement with the Rebels and initiation in the Force are a departure from Luke already, let's see what the writers can innovate in her training and forward.
In a final note, this coming from Disney, I was pleasantly surprised by the movie's darker nature. It's PG-13 just like the previous Star Wars movies, and there's no gore but still the violence is more realistic... and then, there's that strong parricide scene. (ROTJ doesn't really compare to that: good defeats evil not the opposite; Luke fights Vader but doesn't kill him; and the whole thing ends in redemption for dad.) I'm happy that I only took my 9.5-yo boy to the theater, not my almost-7yo daughter whom I had allowed to see the other six movies; even for my son, the movie was only borderline appropriate, and only because I know him to be particularly mature for this material.