I'll grant that the three leads exhibited maturing as actors in Empire. I frankly preferred the chemisty between Leia and Han in Star Wars as the classic antagonists who are quite attracted to one another. The same routine did not work in Empire for me because Leia was no longer smart-alecky, but merely angry and downright mean.

Yes, when she warmed up to Han, the love chemistry between them was great. Perhaps the screenwriters had her be so nasty just so that her warming up would register more strongly. Bah. I think they blew it. Till the kiss, she was a complete bitch. Again, I think the screenwriters mistook wiseguy banter for nasty childishness. I forget the name of the couple whom George brought in to do the 40's-era dialogue between Han and Leia for Star Wars, but he should have brought them on board again for the sequel.

Still, I will not deny the chemistry between Han and Leia in Empire, and I think it was there in
Star Wars, too. But what happened to them in Jedi? I felt zip between them (eh, Harrison Ford was phoning it in for the final installment).

The dialogue was, at best, uneven in The Empire Strikes Back. Lando got some great lines, Yoda had good dialogue, Han Solo's lines were fine. But Luke, Leia and C3PO got shafted in the dialogue department, in my opinion ... and (sigh) it's one of the many drawbacks I find with that most popular of Star Wars films.

edited to add :
Padme loves Anakin vs. Leia loves Han is but one of the many obvious ways in which the prequels fall tragically short of the originals. Far more effort for far less result. Feh.

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