Even though the Indy films are 30,000+times-better than the SW saga combined, I think SW is classic because:
1: It made an undeniable effect on Hollywood, and blockbusters have never been the same since.
2. The special effects are absolutely incredible. I-N-C-R-E-D-I-B-L-E! And don't forget John Williams Einstein-genius score and Darth Vader, possibly the most famous villain of all times (besides Satan).
3. One hell of a cool story, the lightsaber, wonderful actors (prequels not included), awesome alien creatures and spaceships, the lightsaber, a despicable character in Palpatine, the lightsaber, Boba Fett...and did I mention the Lightsaber?
Yes I am in love with lightsabers. Throw one in a movie and I will be happy.
Now Indy is classic because:
1. The good ol' spirit of adventure and delightful action sequences beside an intriguing story.
2. Terrific acting from all parties (go soak your panties, Capshaw haters!), fall-down-and-can't-get-up-funny humor, and by far the coolest adventure hero ever to exist in a movie.
3. Steven Spielberg as director. 'Nuff said.