I wasn't even a twinkle in may parent's eye in 1975. My brother was just being born though.
I think that movies like Shrek and Shrek 2 only get better with time. The first time you see the movie, you are worried about how it is going to end (even if it ended predictably). Without knowing how the characters will be resolved in the movie, you aren't able to "let go" as much and just enjoy the little bits of comedy that are present. I often find this to be the case with comedies - especially like this one - where the story is basically just a vehicle for either (1) laughs or (2) eye candy.
While the story is nice, ultimately, it has been told before - if only in a different way. On second viewing, I anticipate the movie to be funnier, more enjoyable and more memorable.
I enjoyed both movies in the theater, though, first time I saw them. I only came to really love the movie after it came out on DVD.