I watched the prequel trilogy this week (I think I watched them once before about 10 years ago) with my 8 year old and I thought they were pretty good. Maybe that's because I'm not a Star Wars nerd and my entire knowledge of the Star Wars universe is in the 7 films I've seen. Or maybe it is because I see so many fanboys talking about how awful they were.
- Dialogue that even Samuel L. Jackson, Ewan McGregor, Christopher Lee, Natalie Portman, and Liam Neeson couldn't make sound believable.
- Terrible acting by young and old Anakin
- Fart/Poop jokes
- Jar Jar Binks and Boss Nass
- Too much reliance on CGI/CGI that hasn't aged well
- Vader saying "Noooooooooo!"
- No chemistry between Anakin and Ewan (I felt like Finn and Poe had a better bromance in 5 minutes of screen time together)
- No chemistry between Anakin and Padme
- Killed the best bad guy in the first one then shoehorned in Dooku and Grievous
- boring politics
- overly choreographed light saber duels
That's all I can think of off the top of my head
The original and special editions of the OT had some annoying things too though, but nowhere near as bad as the prequels.
- Ewoks set RotJ back from greatness for me
- the Cantina song and dance routine in the special edition RotJ makes me cringe
- Han shot first
- showing Jabba in Ep 4 ruined the mystery revealed in Ep 6