A remake is not a second season.
What I mean by remake is starting over the same project with major/moderate changes.
Like for example, if an anime starts incredibly good but becomes dull as hell later, or if the anime is adapted very poorly. Or even remaking an anime with bad art into one with a good art with the same story, etc.
I think Pandora Hearts and Tsukihime deserve a complete remake.
Tsukihime's visual novel is good as hell, yet the studio ruined the entire story. Animating such a long visual novel in a only 12 episodes could be considered a challenge, but Tsukihime anime adaptation just mocks every Tsukihime visual novel fan. "Yeah? You want your favorite VN to be animated? Okay, take this! Its an anime that's almost nothing like Tsukihime. AND WE EVEN PUT AN AMUSEMENT PARK FILLER EVEN THOUGH WE'RE SHORT ON EPISODES."
Mostly because of this, there's a popular quote among Tsukihime fans-- "There is no Tsukihime Anime."
There needs a goddamn remake of this masterpiece. I'm pretty sure there would be lots of fans if it is animated properly with that epic storyline.
Pandora Hearts is an another anime with similar condition. The manga is too amazing with all the suspense and action, but the anime just wrecks it.