I'm sort of crazy when it comes to re-watching, I like re-watch long runners.
I have watched DBZ 2 times 1 eng dub, 1 time eng sub. Naruto 3 times, shippuuden I have re-watched almost everything. One piece my favorite long runner and one my all time favorite animes , first time i saw it , it was 150 episodes strong started downloading it every week second time it was 220 episodes 3d 390 and now I'm at it again I'm currently at EP 209. I was thinking of re-watching Bleach sometime soon to.
But I have also re watched smaller Animes, like Kenshin, Love Hina, Flame of Recca, Scryed, Cyborg 009, Trigun, And Vandread (one my favorites) like 5 times... and a lot more. I'am ofc watching new ones to but to me animes have a high re-watch value.
Re-watching makes me feel like I get better knowledge about the story and characters, the first time around you focus on cool stuff like fighting and hot babes, and when re-watching I can focus on background story and characters.
EDIT: Damn it now I feel like watching vandread again....