I am an avid reader of Harry Potter and Twilight fan fiction.
This space recommends some exceptional stories. In my favorites you'll find:
Altered and alternate universe writing
Stories with LARGE scope
Characters with POWER
Happily Ever After endings
Outrageously Good Stories
From the many thousands of fanfics, there are a few exceptional stories. Some of those listed here tickle my personal fancies, but all are notable for excellence in writing that I usually only find in the professional world. Unless noted 'in progress', all are complete.
Harry PotterHarry Crow, by robst. What if Harry was raised by Goblins? And instead of growing up as an abused child, was loved and cared for? Why are the Goblins willing to do this, and how does this change the magical world? Superb! A Marauder's Plan, by CatsAreCool. After escaping execution at Hogwarts by dementors, Sirius doesn't run away. Instead he claims his heritage as the Black Head of House, and maneuvers the Ministry to get the false charges overturned. He does this expressly to gain custody of Harry, and sets about protecting and nurturing his godson. A terrific character study with loving and humanistic people, built within a sophisticated and well-developed plot. Harry gets a real family and experiences love, whom then support him as he comes into extraordinary powers. Introduces a unique kind of magic, centered on the Ancient and Noble Houses. A Black Comedy, by nonjon. Wry humor, intelligent character development, and great plot. Harry follows Sirius though the Veil in the Department of Mysteries. Browncoat, Green Eyes, by nonjon. An unexpected and wonderful crossover, where Harry puts himself in stasis and wakes up in the universe of Firefly. What has happened to Earth, and to Magic itself? Can this old and wise mage heal River Tam, a seriously powerful but damaged young woman? And can Harry really fit in with the wacky wild crew of Serenity? Harry Potter and the Methods of Rationality, by Less Wrong. What if Harry is first and foremost a scientist, and when he learns of magic, applies his rationality to make sense of the craziness? Delenda Est, by Lord Silvere. Superb AU where Harry goes into the past, and becomes closely associated with Bella Black. RuneMaster, by Tigerman. Harry discovers Runes, and becomes a powerful master of Rune-based magic. Great plot, endearing characters. The Arithmancer (complete) and Lady Archimedes (in progress), by White Squirrel. Hermione becomes a Master of Arithmancy, effective and significant in her own right. The Accidental Animagus (complete) and Animagus at War, by White Squirrel. Harry escapes the Dursleys though accidental magic. Harry Potter and the Dimensional Trunk, by Ophiuchus. Harry steps into compressed time, and uses the time afforded for training. Time to Put Your Galleons Where Your Mouth Is , by Tsume Yuki. Harry is the Master of Death, reborn again and again, across time both forward and back. And then he is born the Heir of the Ancient and Nobel House of Black, older brother to Sirius and Regulus, and nemesis of Tom Riddle. Powerful Harry, reborn as Turais Rigel Black. Poison Pen, by GenkaiFan. Who is Oliver Twist, and why is he exposing the foibles and hypocrisy of the British magical community?
TwilightOsa Bella, by Myg. Terrific story with sophisticated, well-developed, and engaging characters. A lovely, very original AU. Downward Spiral, by content1. Based on a story premise by Crmcneill. Extraordinary development and dynamic range for many characters, where from the darkest of places, Edward is almost completely destroyed, but recovers and excels through the greatest virtue. Superb! Harvest Moon and Full Moon Rising, by content1. Huge scope, eventually incorporating multiple mythologies and Old Testament personages. Tremendous development of Edward (again!) and other characters. If you don't take practical jokes well, skip chapter 47 in Harvest Moon. From the Wings; Places, Everyone!; and Lights Up! by LJ Summers. One of our best and most prolific Twilight universe authors. Wonderful writing! Waterfalls and Everlong, by SydneyAlice. Sweet, AU with canon couples. Beyond Time, by Tkegl. Creature of Habit and Creatures of Habit, by EZRocksAngel. American Vampire series, by Just4ALE. Once Bitten, Twice Shy, by CertainShadesOfBlue. Broken Doll and From the Ashes, by RowanMoon. Falling Beyond Redemption, by Aleeab4u. Dark, powerful, with native magics and righteous anger expressed. Evermore Experience, by deJean Smith. Intelligent, fun, and romantic. Quality writing, original story, and canon characters plus a couple new ones. Beneath the Surface, by My-Bella. All Human, with teeth. This author really knows how to write character-based stories. Also check out her trilogy one series that starts with The Fairytale Continues. Good! Elemental, by TallulahBelle, an AU based on a premise surrounding elemental magic, repurposing all the characters and creating something different and refreshing. Wonderful. Make Haste My Beloved, from a great family tree of intertwined stories under the heading Unforeseen Events, by jmolly. In progress...A Twilight alternate universe with joyful, intelligent, loving, interesting characters, huge scope, and a villain or two. If the author finishes the series, this will probably be my favorite of my favorites. There is so much love in these stories, I can only hope...
Many of my favorites could be brought up top for special attention, but not all. Here's why.
The Never Ending Story
There are a few star-brights that I doubt the authors will complete. Disappointing. I guess many writers do not flesh out their ideas before they begin publishing, and then life comes to interrupt a good thing.
Too Much Citrus
I suppose it is a matter of taste. Some stories have so much sex, it's nearly never-ending. Gah! Too much of a good thing. There's more to life than sex.
However, a few stories in my Favorites are excessively carnal. Why are they here? Because the writing is so darn good, I can't let them go. I won't publish names alongside this complaint—you have to make that evaluation on your own.
Needs More Beta
There is at least one story in my favorites (below) that has many word usage, grammar, and spelling errors. In a very few special cases, I'm willing to overlook ridiculous errors like "we said our vowels together" (vows), and words like defiantly when the spelling is supposed to be definitely. I almost never tolerate this sort of carelessness, but when I find that stuff in an otherwise compelling and enjoyable complete story, I will occasionally break my own rules. I beg forgiveness for making any such story a favorite, and ask you to make your own decision. Apparently many others like the particular story I'm thinking of—it has several thousand reviews.