I agree that Wayne's World 2 is great as well, partly because it didn't try to just repeat the first movie. Sure the tension with Cassandra and Wayne in both movies is similar, but overall, the main plots were different enough that WW2 wasn't just a rehash of the previous film. It had a unique arc and introduced some new characters.
It also kind of turned the sterotypes of the slacker on its head, as Wayne and Garth seem like slackers when we first meet them, but through the course of both movies, we see them work really hard on what they love. It seemed to be a way of saying that Generation X may come across as lazy and apathetic, but there are things we care about and when we put our minds to it, we're going to do great things that connect with the people of today. In both cases, I think the success of both movies is a testament to the characterization, as we actually cared about Wayne and Garth.
Most of the jokes/gags are pretty timeless, as well. I feel too many comedy movies try to be relevant by mentioning/parodying as much of pop culture as it can. The problem lies with the fact that what's funny at the time won't be funny years later. Even the product placement joke that references the late, lamented Nuprin still makes sense, even if you haven't seen those commercials, because Nuprin isn't the joke, it's a part of a larger scene with enough context that you can laugh along with it. They were very clever in what they chose to parody, because it's largely what's still relevant today.
