Finally got to see it today and I'll echo the previous sentiments: it was outstanding 20 years ago and it is outstanding today! Noticed a lot of details in the sets that I had forgotten over the past two decades (or hadn't noticed at all before).
Since others have pointed out the great writing, performances, special effects and directing, I'll take sound. The movie is loud when it needs to be and not just for the sake of being loud. I saw it several times in the theater during the first run and I had really forgotten the emphasis on the t-rex roar and the raptor's screeching.
The t-rex attack scene definitely holds up (and may be one of the best "action" sequences in movie history) but when it cuts back to the crew in the computer room everyone in the theater exhales at the same time just like they did 20 years ago.