So, like most terms on ATRL, what is "pop" isn't completely defined, so some artists are called pop by some but not by others. The question is then, do you consider the following artists pop acts or not. The list is what came to my mind, so feel free to out other people not on the list as pop acts if you think it necessary.
You're pop if you're popular on the radio and you're music isn't strictly one thing or another.
none of them are pop. the only ones close enough are Adele & Marina. But they both have so much music that would never see the light of day on popular radio.
Adele would only be considered pop because of how successful and how much impact her music made on pop radio.
Marina would only be considered pop because of a few songs from her latest album like "radioactive" "primadonna "bubblegum bitch" "hypocrates" "lies" and "homewrecker." 6 songs out of the dozens she's written/recorded. She's not a pop act. Although that's what she's trying to portray now.
They all are except for Azealia. Adele is the most pop, with some R&B influences, and I'd say Ellie is close to pure pop too. The rest are more alternative pop.