One thing's clear about "Womanizer"...it sounds exactly like Rihanna's "S.O.S."! It also kinda sounds like "Radar," off Britney's Blackout.
Doesn't it also seem like that bridge to the chorus is a bit lyrically-challenged? ("Womanizer, womanizer, oh, you're a womanizer, oh, you're a womanizer...")
Did Britney write this gem herself?