Being memorable doesn't make it good. As someone that went through all 6 films in a relatively short time-span not so long ago, I can't personally say the dialogue was any better in the originals than it was in the prequels.
"I have a bad feeling about this"
Hehh...
The original SW movies had a few good quotes. Lot of them from Harrison Ford or Alec Guiness. But that's about it.
But yeah, overall, the dialogues in these movies were cringe worthy.
In fact, Lucas writes dialogues that are fit for robotic characters. So anytime a robotic figure is involved, the cringe factor goes down a bit.