* Have at least some baseline modicum of talent * Have access to talented songwriters * Have access to talented producers * Be attractive, or at least interesting to look at * Have a stage presence
Bonus points for: * Ability to dance * A salacious or intriguing "private" life
Many pop stars have singing talent in spades (Beyonce, Adele, Whitney Houston), but many others have proven that extraordinary singing talent is not a pre-requisite for enormous success (Britney Spears, Jennifer Lopez, Miley Cyrus, perhaps Madonna).
I would say talent is less important now than ever. But this could be an illusion, as history is likely to forget pop stars who leave behind nothing memorable.