There are plenty of great actors and outstanding performances in the Prequels. Ewan McGregor, Christopher Lee, and Ian McDiarmid are a few examples of actors who stand out in the trilogy. And the performance of the other actors is enjoyed by more people than given credit for. Many children grew up with Hayden Christenson as Anakin and liked him in the role.
The Sequels are not immune to bad dialogue either. "Saving what we love" and "They fly now?" stand out as ridiculed lines from the movies. And even if the actors were good, the characters usually weren't. Rey was not nearly as memorable a protagonist as Anakin; Snoke was such a bad villain they ended up going back to Ian McDiarmid as Palpatine anyway.