Once they made it out of Rivendell, LOTR really piked up. I just wish gandalf would shut up sometimes, and how come whenever they meet someone, they have to exchange life stories and talk about Shadowfax for two pages? HP was meh, but LOTR was one of the best books I have ever read.
The Bartimaeus Trilogy is both funnier and better than both LotR and HP. Anyway. I don't think you can compare those two series. LotR being somewhat epic in the genre of fantasy and very important to the early beginning of roleplaying, and HP being a modern tale of fate and magic. Both tales have some faults and some goodies, but not really comparable, since they are too different, and have fans all around the world.