Snoopy does for the Peanuts what Hit and Run did for the Simpsons. An all around excellent title.
Even if the gameplay didn't hold up, it would be difficult to dislike a game that does such wonderful justice to its source material. Snoopy is pitch perfect: From the music to the visuals to the voice acting, it would be difficult to do greater justice to Charles M. Schulz's vision. The dialogue is the funniest and most well written I've heard in a game since Tim Schaefer's Psychonauts.
And boy does the gameplay hold up indeed! In many ways, this game is better designed than more "serious" historical flying games like Blazing Angels or Heroes of the Pacific. Snoopy's mission design is excellent, with tasks ranging from good, simple fun to the surprisingly complex. It does sometimes become a little too arcade-like for my taste, and of course it would be silly to expect historical accuracy (giant drilling robots in WWI?), but such minor quibbles hardly mar what is otherwise an altogether solid flying adventure.
If you're a Peanuts fan or a fan of flying games (or both), you have no excuse for not picking up this title.