Gaga. I think it's not so much her fault though as much as the dance trend having been really thoroughly put through the wringer. Katy and Rihanna tend to explore more enduring soundscapes like rock and R&B/urban (respectively), which helps in giving their music a little more lasting appeal.
LMAO what people actually voting Gaga even though her music is the least dated out of all three? Its clearly Katy her cheesy bop sounds is something that will forever be stuck in 2010.
There are almost no albums more dated than Music of the Sun (and, to a lesser extent, A Girl Like Me) However, the rest of Riri's discography is holding up pretty well minus a few tracks here and there.
Gaga's stuff has aged a bit, but it's still solid and easy to listen to.
Most of Katy's tracks were dated on-release, and the years have only made them worse.
Teenage Dream is generic but that doesn't mean its not completely timeless.
