Same here. I'd never seen parts of it on TV or anything until I watched it for the first time, since I'd seen it was ranked #1 on IMDB. There wasn't anything about it that made me feel like it was the best movie ever. The plot was very conventional, the shots were fine, the performances were pretty good - it seemed like a 7-8/10 movie, there are lots like it. Then I watched Lawrence of Arabia and 2001 and I got the "best movie ever" kind of feeling from them - great cinematography, big themes, bombastic soundtracks. But I can see why Shawshank could be the least controversial movie of all time, it's fine at everything and that helps when there are so many people ranking it.