1. The protagonists Naruto & Harry were both orphaned as babies when their parents died protecting them from an evil force that was destroying their town/world.
Baby Naruto and Baby Harry Potter survived the attacks of Nine-Tails and Voldemort, respectively.
2. Both heroes have physical markings on their faces from their lasting connections with the evil creature who killed their parents.
Naruto - Whisker marks across face
Harry Potter - Lightening bolt scar on forehead
3. Both Naruto and Harry have a piece of, or indeed the whole of, that evil creature now living inside of their own body.
Naruto - "After causing untold death and destruction, the Nine-Tails was stopped by the village's leader, the Fourth Hokage, who gave his life to seal the Nine-Tails into the newborn Naruto Uzumaki". (source)
Harry Potter - Harry is Voldemort's final, unintentional horcrux; the curse meant to kill Harry actually rebounded, destroying Voldemort's physical body and causing a piece of his soul to latch onto and remain within baby Harry.
Furthermore, neither Naruto or Harry was even aware of the evil presence trapped within them for many, many years. It was kept a secret from them - a difficult decision made by the school/community leader who would later become their friend and trusted mentor (Dumbledore for Harry, 3rd Hokage for Naruto).
4. Both orphans grew up very lonely, shunned by their society/entrusted guardians out of fear.
Harry Potter suffered neglect and verbal (and sometimes physical) abuse from his entrusted guardians: Aunt Petunia, Uncle Vernon, and cousin Dudley. They feared (and envied) his magical capabilities, while also resenting the 'obligation' of raising him. He grew up in a cupboard under their staircase, with no love, attention, or real information about his family.
The Hidden Leaf Village that Naruto grew up in mostly shunned him - the adults fearing and mistrusting the fox lying within him which had just destroyed many lives and most of their village. However, the entire town was forbid to discuss the Nine-Tail fox incident and/or tell Naruto the truth about the beast within him, so Naruto never even knew why he was being shunned.
5. Both series' protagonists (Naruto/Harry Potter) are part of a trio of friends which fights and grows together in friendship throughout the series. Both trios include 2 males and one female. In both cases, these are the first real friendships they've ever had, and remain their most significant.
Interesting to note: In both series, the female is bookish, stubborn, and ultimately crushes on the other male in the trio.
Harry, Ron, and Hermione = Naruto, Sasuke Uchiha, and Sakura Haruno
6. Primary antagonists both have snake-like appearances after meddling in dark, forbidden (magic/jutsu) techniques to increase their power and escape death. Both command snakes.
Voldemort - "tall and skeletally thin", with a face "whiter than a skull, with wide, livid scarlet eyes and a nose that was as flat as a snake's with slits for nostrils (as described by J.K. Rowling). He can speak parseltounge thus communicating with snakes and has a snake for a companion named Nagini within whom a piece of Voldemort's soul resides.
"Orochimaru is heavily associated with snakes: his personality, appearance and even name are snake-like or orientated. After many experiments and forbidden techniques, Orochimaru's true form indeed became that of a snake. Orochimaru was also able to use senjutsu, and with this knowledge he developed the cursed seals." (source)
7. Both heroes' mentors, who also were also the appointed leaders of their communities, sacrificed themselves to defeat evil.
Both had an elderly, wise, grandfather-looking mentor who was the leader of their school/training, who lead in the fight for good, respected tradition and honor, and who absolutely adored their students. Both died fighting to defeat evil - their friendships with these mentors and their deaths impacted Naruto and Harry forever.
Sadly these aren't the only mentors who Naruto and Harry have lost....
Harry Potter lost Albus Dumbeldore, Sirius Black and Remus Lupin
Naruto Uzumaki lost 3rd Hokage (Hiruzen Sarutobi), Jiraiya and Asuma
8. They both attend an academy where they are trained in magic - or for the ninjas, in chakra techniques - complete tasks as teams, sometimes compete against other schools, and train under quirky professors/sensei.
"Much of Harry Potter takes place in Hogwarts, where students are divided into groups and occasionally compete with other schools. Quirky teachers litter the landscape and some are harsher or more unconventional in their teaching methods than others.
Similarly, Naruto takes place in Konoha village, where students are broken up into teams and occasionally compete against other villages. Each team is assigned a quirky teacher with a unique back story and individual teaching style." (source)
9. They've both shown great promise from an early age, exemplify unparalleled loyalty, and a stubbornness to succeed - even though neither is considered exceptionally gifted or naturally brilliant in comparison with their peers.
Quite impressively, both Naruto and Harry Potter mastered at least one extremely difficult technique that was thought to be far too advanced for their age and even fully-educated Wizard/Shinobi Ninja.
Harry - Patronus Charm
Naruto - Multiple Shadow Clone & Rasengan
10. Both have hot tempers and are serial rule breakers; neither usually strategizes before jumping into battles - but both display great problem solving and creative decision making skills in battle.
Both are characteristically kind and loyal - willingly risking their lives time and time again to protect loved ones and whatever underdog needs protection.
I'm guessing many more of you have watched the Harry Potter movies and read the HP books than those who've watched the Naruto animation series or read the manga. To those fans, I encourage you to "branch out" and give Naruto a shot. As you can see, the stories' fundamentals are shockingly similar. More importantly, the characters will give you major feels and occupy a place in your heart, always.... As any great story should.
PS - Story recommendation mixing anime, magic & zombies: ZombieCON
THANK YOU J.K. Rowling and Mavashi Kishimoto for bringing us these beloved, enrapturing worlds.