It’s not that Lady Gaga’s a plagiarist but that she’s nothing remarkable especially when you bring up other musicians that have done similarly. Charlotte Church was also classically trained, Alicia Keys can also play the piano and Michelle Branch has done the rock chick thing before. Likewise a female musician with a golden voice that struggled with anorexia and drugs would easily have been Marianne Faithfull.
But it’s easy to dismiss them for being irrelevant and likewise Sarah Geronimo’s a good example of a pop diva that’s successful without being sexualised. Natalie and Mylene Farmer have been rocking the successful pop songstress/songwriter thing before but all three women, though popular, are too foreign. As what somebody else said, Gaga’s real appeal lies in being different without being too alienating.
The other three have their own merits but it’s easier to overhype Gaga even if she’s nothing special in the long run. Perhaps people are wary of Gaga because she tends to get overhyped at the expense of others who are just as good and successful as she is. Even if they’re successful in their home countries.