For some reason, it surprises me how many people weren't alive when the original Star Wars came out. I really don't know why, I think it's just one of those weird age-ism things like how it always struck me as "weird" in high school the idea of being born during the 80's.
Anyhow, I was 24 when TPM came out. That put me at a measly two when Star Wars came out, but I still got to see it in the theatre thanks to a double-feature with Empire sometime in 1980-81.
The best theatre Star Wars experience for me, though, is without question Jedi. May not be my favorite of the movies, but I got to see it in a classic local theatre (sadly long gone) complete with balcony and ice-rinky floors resulting from years of spilled, buttery popcorn.