The anime form isn't the "original", but itself an adaptation of the manga. I don't have a huge problem in principle with media forms being adapted into other media forms, though, so that isn't really a knock against it. Imo whether an adaption is good is more interesting than the status as original/adaptation/remake. Some adaptations and remakes are good!
Yes, the original format is manga, and I have a few volumes -- the overlap is remarkable. As if Madhouse studios took the pictures, enhanced them, gave them a flow and breathed life into them with excellent voice acting and music.
The manga is outstanding because of the plot, but nothing beats the anime.