I beg to differ...
Kanshou & Bakuya - Fate/Stay Night
Sword of Fanelia - The Vision of Escaflowne
Better Half - Hataraku, Maou-sama!
Armstrong Family Sword - Fullmetal Alchemist
Gravity Blade - UQ Holder (Manga)
La Pucelle - Fate/Apocrypha (Light Novel)
Balmung - Fate/Apocrypha
Griffith's Sword - Berserk
Saya's (First) Sword - Blood+
Most swords - Ubel Blatt
Amon's Royal Sword - Magi the Labyrinth of Magic
Murata-tou - Highschool of the Dead
Derflinger - Zero no Tsukaima
Watou - Rurouni Kenshin
Li Syaoran's Sword - Cardcaptor Sakura
Sayaka's Cutlass - Puella Magi Madoka Magica
With the exception of that last one, all of them are just those that are in series I have personally seen/read, which is but a small sampling of all the manga & anime available. A better statement would have been "the most popular shounen series and a number of fantasy video games have either ridiculously oversized or painfully generic swords".
what kind of sword are Kanshou & Bakuya?