I like the idea here, but in the end it left me wanting. The block party and the movie were both a way to celebrate the city (and cities more generally), but in the end much of the movie is composed of straight-forward shots of the bands performing. In this case, since I only liked a few of the songs, much of the time I was just waiting for whoever might come on next. I bet it was more fun to be there than to watch.
Block Party isn't just a concert film or a documentary about an event, it's a celebration of humanity. Chappelle and Gondry are genuinely interested in all the weird and wonderful people they encounter, and that warmth elevates the film to greatness even before Dave reveals some of his philosophy about comedy and music. It's pure joy.