for me, Like A Prayer is her first proper studio album. even if its sonically diverse, there is an absolutely strong cohesion on the lyrical content: love, romantic love, matrimonial love, spiritual love, self love, juvenile love, family love, humanitarian love, sexual love – do you believe in love?
on the other hand, Madonna, Like A Virgin and True Blue are single collections without much cohesion. yes, there are some iconic moments on their singles, but it's safe to say the bar really drops on the album tracks. Like A Virgin being the worst offender as you would really expect more from a Nile Rodgers production and also the fact Into The Groove, Crazy For You and Gambler were not on it.