Fanon: Most of the fandom views White—Victini and Zekrom as the "canon" version, since Ash being the Hero of Ideals is much more in character for him then the Hero of Truth. This is also consistent with the anime's Story Arc pertaining to the legendary dragons having N as the Hero of Truth and noting a connection between Ash and Zekrom.
Hype Backlash: When the (dual) movie was released, it generated quite a bit more hype than usual - possibly due to the popularity of its namesake games and the anime series appearing to get a bit better at the time, as well as the dual-movie gimmick and limited US theatrical release. Now the movie's largely been forgotten, and especially isn't considered to be up to the standards of the better movies in the series (including its immediate successor).
They Wasted a Perfectly Good Character: The earliest promotions for the films advertised the child characters as each being exclusive to one of the films, Luis exclusive to Black and Luisa exclusive to White. In the finished product, both characters are in both films and don't really do anything in either.
Woolseyism: The English titles. In Japanese, the names are 'The Black Hero: Zekrom', and 'The White Hero: Reshiram'. In English, the colours are swapped, so now each of the dragons are associated with the opposite coloured movie, so Reshiram is now the mascot of the Black movie, and vice versa, which matches up with the mascots of the games themselves. This also matches up with Damon's Pokemon, as in Black, he has a Gothitelle, and in White, he has a Reuniclus, each of which are exclusive to the game that shares a name with the movie.