Disagree, they have similarities but they have their own unique styles. Its like music genres, its all music but they have their own unique styles which separate them.
How are they the same? Manga is a form of comic, but is read from right to left, and is a whole different type of material. Same goes for anime. Anime was based on Disney cartoons, but it's not a cartoon due to obious differences.
anime and cartoons are the same thing they just come from different geographic locations. It's like people who try to say they read "Graphic Novels" No mother****er you read comics. The only noticeable difference between a comic series and a manga series is the manga writer is usually the artist as well and does not leave the work where as comics employ separate writers and authors and writers change every so many issues.
The general themes and delivery processes(manga weekly comic bi-weekly or monthly) may be different but they are still the same concept, animated story telling.