I've only seen the first one (American Pie), and I thought it was absolute shit. It relies on dumb immature sexual humor and little else for laughs.

It is about a group of high school boys making a pact to lose their virginity, and the misadventure and awkward over the top hilarity that ensues on their quest. So yeah, if you are 14, or an anti-social virgin of any age, you might find it really awesome.

I agree with Fink, Austin Powers is vastly superior to American Pie, and I pretty much can't stand Austin Powers. But at least the first Austin Powers has some genuinely funny moments and is a parody of something other than just high school sexuality.