It's a little unfair to rank the films on their own because they come together to form a greater saga, but don't lie, you have a favorite. This thread is just for fun, so if you think it's stupid, just don't participate.
For me, it goes like this:
1. A New Hope - The original movie is still my favorite. I'm a prequel kid, so I wasn't around yet when the OT came out in theaters, but I did start out with ANH on VHS and it left its mark. I love this movie. On its own, it's a pure self-contained adventure story in an imaginative setting, and as a part of the larger saga, it's an invigorating look at the Star Wars universe from a new perspective (after three movies from the perspective of the Jedi) and an introduction to the best leading cast of all time. 10/10, perfection.
2. Revenge of the Sith - The tragic tale of Anakin's fall to the Dark Side delivers on all counts. It's the darkest entry in the Star Wars saga, but that's not why I like it so much. I like it because it's the most well-crafted, tightly focused of the three prequels, and an immensely satisfying transition from the opulence of the PT to the stark "used future" of the OT - not just visually, but tonally as well. Seeing the Star Destroyer in the first shot of ANH right after witnessing the events of this movie is a masterstroke. It really drives home the tyranny of the Empire. 9.5/10, incredible.
3. The Empire Strikes Back - No, I'm not being contrarian by ranking TESB in third place. I love this movie. I just happen to love ANH and ROTS a little bit more. Anyway, TESB is an incredible brooding masterpiece and it stands alone in the Star Wars saga as a movie that puts philosophy and introspection on center stage. In the context of the complete saga, it is a necessary breather that expounds upon the nature of the Force and prepares the audience for the grand climax of ROTJ. 9.5/10, incredible.
4. Return of the Jedi - What a climax ROTJ delivers! The first act is a little detached from the rest of the film, thematically, but it does serve several narrative purposes and doesn't feel too out of place. Plus, it's a hell of a ride. The final showdown on Endor is amazing, and the stuff between Luke and Vader is some of the finest writing in the entire saga. 9/10, amazing.
5. The Phantom Menace - This was the first Star Wars movie I ever saw in theaters! I loved it that day, and I still love it 16 years later. The movie does have some weird pacing issues, but thankfully they're not very distracting. (It took multiple viewings for me to even notice them.) I've never had a problem with Jar Jar Binks. He's not a favorite of mine, but he's certainly not a bad character and I don't think his presence hurts the movie. 8/10, very good.
6. Attack of the Clones - This is a unique film for me because it's the first time I experienced Star Wars as a die-hard fan. I spent months speculating about the movie online before its release and hungrily consumed as much of the marketing as I could. (I bought a ton of the tie-in merchandise too.) The film itself is good, but not great, and it's the only Star Wars movie that makes me feel that way. The romance is the problem. It just wasn't convincing to me. It needed to be better acted (or perhaps better directed?), particularly since it's the focal point of the movie. However, I love the Obi-Wan detective story, and the climax on Geonosis is one of the best that Star Wars has ever done. My #1 favorite is still ANH's Death Star trench run, but this is a close second. Plus, Natalie Portman looks smoking hot in her skimpy little outfits. Because of this movie, I had a huge crush on her for the entirety of my teenage years. Hell, I still have a huge crush on her. Ultimately I have mixed feelings about the film as a stand-alone piece, but it works very well in the context of the larger saga. I have to give this one a 7/10, which is merely good, but I do enjoy the movie a lot. The romance is what drags it down so much. Honestly, I was tempted to give it a 6/10, but the other parts of the film hold up very well.
NOTE: I'm a tough reviewer and I use a harsh scale. I don't give out 10/10 scores lightly. A 5/10 is average, not bad, so keep that in mind when you're looking at these scores.