As Star Wars films, they're atrocious, badly-written pieces of money-grabbing junk that was in serious need of a better set of executive producers (or just a script editor) to tell Lucas when his script made no sense. Which was all the fucking time.
As sci-fi fantasy films, though:
Episode I is poorly written garbage, but at least has a 3-act plot structure that, while meandering around, has a lot of bright colours and an exploration aspect that is quite nice. Not incredible, but a ride nontheless.
Episode II relies on good acting to let the romance plot be the crux it needs to be. Which is why it's so lucky that the acting was... completely atrocious, with absolutely no chemistry between the leads, with a horrible "tell don't show" policy applied to everything that happened between Episode I and here, and... well... Lucas just doesn't know how to write a love story. It's like he read the screenplay of Romeo and Juliet and thought it was the most contemporary, up-to-date vision of love imaginable, so he shoehorned Shakespearian-era dialog into what is existentially a modern love story. Weakest Star Wars film to date.
Episode III isn't bad; see comments on Episode I, then but it under a black filter. End fight scene didn't need to be 50 minutes long. Star Wars-related note: Darth Vader shouldn't have been the be-all end-all puzzle piece to the universe (to quote Red Letter Media). Not a terrible film, it too was a ride like Episode I was, so it works.
Like I said, though. As Star Wars films, it basically fucks up the entire backstory, makes a lot of the religious ideology of the "original" trilogy redundant, reduces what was once a 3-dimensional universe full of real people into a 2D universe full of creepy alien monks with no emotion. Also did I mention the script never made any sense? Yeah.