This.
Brock has always been one of my favorite characters, so seeing him leave was a huge disappointment for me. His constant obsession over girls never got old to me, and they always had some sort of way to pull him away from the ladies, be it Misty or Max pulling him away by the ear or Croagunk using Poison Jab. He's also just always kind of been the one to watch over the group and act as a sort of older brother to them, seeing as he has experience with this having to take care of all of his younger brothers and sisters.
Cilan is all right at times, and there are moments where he makes me laugh, but most of the time he's just very annoying. I personally don't care for his "evaluation time" thing.