"American Pie" does have some elements that could have contributed to make another silly movie, like the gross-out humor, the usual share of T&A, the fouled language, in few words, the typical ingredients of a cheap teen movie.
But "American Pie" has key elements that set the movie apart from its predecessors: the cast is kinda charismatic, some of these actors and actresses will be lost in oblivion and others will be famous, but it's hard to deny that these cast is funny and sure they had fun while they were filming "American Pie". Special mention to Eugene Levy, he brings the wisdom of a veteran, and mixes very well with the young newcomers, of course, he steals every scene that he appears on.
The girls in this kind of movies usually are attractive, and thankfully (to the guys) "American Pie" has pretty girls like Tara Reid, Alyson Hannigan, Shannon Elizabeth and Mena Suvari, not all these girls have real acting talent, but at least in "American Pie" they got the work done.
On the other hand, this original "American Pie" movie is the only one truly worthy in the series. I'm sure there are a lot of fans of the second and third movies, but the most demanding audiences will agree that the only decent "American Pie" movie, is this one, the original.