The magic stuff and basic story elements are fine enough but the bad guy is terribly boring. He's like a villain from Captain Planet or something. "Blast, foiled again because I do not understand basic concepts of love, friendship and turning the water off while brushing my teeth!"
This comment is funny, but I think it misses the point. Voldemort is not the bad guy in Harry Potter, in my opinion. Voldemort is the personification of pure evil. The "bad guys" are the ones that are seduced by Voldemort's (evil's) promises of greatness and power. The worst offender is Bellatrix LeStrange. She is just about as cartoon-evil as Voldemort himself. But all other bad guys are varying shades of gray.
J.K. Rowling does some really interesting things with the concept of "bad guys" throughout her series. We first meet Voldemort in book 1 physically attached to Professor Quirrel. Our first introduction to the "bad guy" has him completely consuming one of his followers. I think this is significant. The true power of Voldemort is his influence over those that follow him.
We see him again in book 2 as Tom Riddle, before he became Voldemort. His "bad guy" status isn't readily apparent, but like in book 1, he only gains power when someone willingly opens up to him. Rowling shows us that even Ginny Weasley, who throughout the rest of the series is completely good (in an awesome, kick-ass kind of way), is vulnerable to Voldemort's power. Ginny's weakness was her insecurity and fear, and evil preys on our weakness. Book 1 shows us that the danger of Voldemort lies in his influence over people, and book 2 shows us how easy it is to allow that influence to consume you.
By the time Voldemort comes into full power, I think Rowling has presented a wide range of bad guys. The Dursleys, Gilderoy Lockhart, Sirius Black, Lucius Malfoy, Peter Pettigrew, Severus Snape, Draco Malfoy, Barty Crouch Jr., Cornelius Fudge... these are the bad guys. But even the worst bad guys have redeeming moments of love, friendship, and loyalty. One of my favorite moments in the series is in book 7, when Voldemort asks Narcissa to see if Harry Potter is alive. She lies. Not because she has any change of heart, but because she loves her son. As Sirius says in Order of the Phoenix, "the world isn't split into good people and Death Eaters." He was talking about Dolores Umbridge, of course. A perfect example of how sometimes the very worst bad guys work for the "good" side.
There is no personification of good in the book. Lily Potter comes close. The power of her love goes head-to-head with the power of Voldemort, and I can't think of any character flaws. But besides Lily, all of the other good guys are just as imperfect as the bad guys. Even Dumbledore has his serious flaws and regrets, as we learn in book 7. The heroes of the book all have their less-than heroic moments: Ginny Weasley opens the chamber of secrets, James Potter severely bullies Snape, Remus Lupin nearly kills a bunch of people as a werewolf, Sirius Black almost causes Snape's death and is extremely cruel to his house elf, Ron Weasley abandons his friends in a fit of jealousy, and even Harry Potter gets so obsessed with the deathly hallows that his carelessness leads to the group's capture, Hermoine getting tortured, and Dobby getting killed. These aren't small mistakes, they are bad enough to make them the bad guys in small snapshots of the overall story.
One of the best things about Harry Potter, in my opinion, is that it blurs the line between good and evil. But it does it in a very subtle way. For the most part, you know the good guys and you know the bad guys. (Except for Snape, until the very end.) Voldemort is not a subtle or nuanced bad guy, but his affect on the bad guys and the good guys is subtle, ambiguous, and devastating. It's what drives the books. How do we deal with evil? What does it look like when we encounter it? Can we recognize it? Can we recognize it in ourselves?
(p.s. In Chad's defense, he's only judging Harry Potter by the movies. I'm sure if he read the books, he'd be totes bees.)