A lot of her earliest stuff is surprisingly good and shockingly depressive.
Teenage Dream the track is a generational masterpiece, the rest of the album ranges from eh to great.
Prism has some high highs (Birthday, Unconditionally) and some reallyyyy low lows I won’t mention
No clue after that, stopped paying attention

One of the Boys is her best and Mannequin is her best song

I really never paid much attention to her or her career. I knew her popular songs, I kissed a girl, Hot n Cold, California Girls, etc. from back in the day, and thought they were alright pop songs, not really for me but they were pleasant to listen to I guess. I only found out last year due to the astronaut shit that apparently she's been hated for a while and her career has been on the decline for a decade, came as a surprise to me I thought that she was still popular, or at least liked.