The original Ice Age film was one of the first I ever actually owned. It was one of the best films I had seen. When the second film then came out, I loved that one too. The films of Ice Age have references for all ages, and when I was growing up, I might not have understood them all at first, but over time I did.
I have watched all four films countless times [the fourth less so, due to it being newer], and each have held a lot of thoughts, and all of them are different depending on which film it is.