I think all of them are purely fun entertainment popcorn films. I never took the films seriously like a lot of nostalgic Star Wars geeks, esspecially the Anti-Prequel Fans. They complain the prequels were too "kiddy" yet the same crap was in the original films (ewoks, jawas, droid comic relief, bad acting), they just filter it out for nostalgia and look at these films as if they are grand epics for serious filmgoers. As Harrison Ford said "Give me a break".
Star Wars - Best of the series; holds well because its the only film you could watch without seeing the rest. 10/10
The Empire Strikes Back - Good sequel, dark and better written. 10/10
Return of the Jedi - Good conclusion to the saga; the special effects are still incredible for today 8/10
The Phantom Menace - A bit too political but has great scenes such as the pod race and ALL the lightsaber duels. 8/10
Attack of the Clones - REALLY bad dialogue in the Anakin/Padme, even for a popcorn film. Has a few gems but is ultimately flawed. 7/10
Revenge of the Sith - Great battles, some better acting, very dark and the ending makes you want to go back to the original and continue the story. ILM really took the f/x up a knotch, it should have gotten an oscar for that category 9/10