A bit rubbish, this.
There are some parts of 'Horton Hears a Who!' that I don't mind, though for the most part I found this 2008 flick to be very boring. Jim Carrey, who I am a fan of, is a let down in this role, the whole side of the story involving Carrey's Horton became so uninteresting to me.
The bits with (the also underwhelming, just less so) Steve Carell's Mayor hold the most intrigue, though the barrage of Horton (also you'd expect, in fairness) meant that I couldn't even get into that part of the story. The rest of the cast, despite some well known names, aren't good either.
I evidently do have an iffy history with Dr. Seuss film adaptations, with only 'The Cat in the Hat' - I know, I'm in the heavy minority with it but don't @ me ๐ - being a film that I truly enjoy. This one is a disappointment, unfortunately.