I got to see Clash of the Titans in 1981 when it came out. My brother took me which is very rare, but I guess even he knew I had to see this movie being that I was so much into fantasy and the like. I still love the movie and it was being shown last week. I sat and watched it and never thought that it was out-dated or anything. Same as if I was watching one the old Japanese monster movies. It's just something that was so cool to watch back in the day and you just have to take the trip back mentally and forget about today's technology to really enjoy these movies when they are shown again.
And really, you're not missing anything if you don't see this in 3D. Save your money.