I believe Iris deserves the title of Champion just as much as anyone else. She won against Alder in a fair fight, unlike Alder who got appointed as champ by the the Elite Four, and she seems to be fairly altruistic (she was helping people she barely knew get back their Pokémon from a Pokémon rights group in Black and White), and as we see in her Memory Link, Iris mentions how people in the Village of Dragons take living alongside Pokémon for granted. Perhaps she was one of these people? It would explain why Drayden brought Iris to Unova in the first place: He wanted to bring her closer to her Pokémon, and Unova would allow the bond to grow, because people truly appreciate Pokémon in Unova. Heck, Drayden could have been pushing her to challenge Alder to help her grow as person, and being Champion would help even moreso. So, she has grown as a person, and her new title shows that.
Also, her team and battle theme is awesome.