You'll never get a second chance to experience something for the first time, obviously. I don't really remember the first time I saw Jurassic Park. It definitely wasn't in theatres, I was too young for that. My parents owned it on VHS, so I probably watched that on a 19" CRT TV. Not exactly an epic home theatre setup, but that didn't matter. There were dinosaurs, dinosaurs which looked real. It was amazing, and has been one of my favourite all time movies for as long as I can remember. Sure, the plot is ridiculous and the acting in mediocre, but it has dinosaurs.
They just re-released the movie in theatres 3D last week, and even though I own it on blu-ray and have seen it a million times now, I jumped at the chance to capitalize on an opportunity I thought I would never again have, and experience the film on the big screen. Obviously it wasn't the same as seeing it for the first time, but it was still excellent. The special effects still held up, remarkably, and the 3D was very well done (subtle but effective). I also noticed things I had never noticed before; the effect of blowing it up on the big screen and controlling all my attention, I suppose.
Well, almost all of my attention. The one negative was the grandparents who brought their young grandchildren (likely 4 and 6) to the movie. When the kids weren't terrified, they were talking incessantly or up walking around, and the grandparents made absolutely no attempt to reign them in. Mercifully for the rest of the theatre, they left two thirds of the way through the film when the kids got scared. Still, it was unbelievably annoying. Aside from the fact that the grandparents have a responsibility to keep the kids in check as best they can, how do you not know at this point that Jurassic Park isn't a good movie for children that young? It's out for twenty years! No excuses for that.