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The prequels are AMAZING. Easily among the best sci-fi and action movies ever made.
Episode 1: Qui-gon, Obiwan, young Anakin, Dart Maul, droids army, Naboo, Jar Jar, war and politics was great
Episode 2: Anakin padawan, Obiwan, the war with the clone, the rise of Sidious, the dark side growing, Yoda vs Doku was great too
Episode 3: Even better, the coruscent battle, Doku, Grivious, the end of the jedis, Anakin turning into Vador, Obiwan vs Anaking, Yoda vs Sidious
All 3 prequels are great.
I will go as far as saying that people who did not like the prequels are not Star wars fans.