In historical context, The General is revolutionary. Keaton clearly had an understanding of cinema as the art form it truly is. There is no attempt to replicate another, such as theatre. Instead, Keaton uses closeups, unique framings, and even some tracking shots to create a wonderful sense of mise en scene (sue me).
Similarly, the film takes great joy in parodying earlier films. In regards to the epic films of D.W. Griffith, the film is a clear disassembly of Griffith's definition of film, choosing to toy with the war and history for its own benefit. In fact, you truly get the sense that Keaton is in full control over this film as he manages to continually heighten the gags, something which, at the time, was a rarity.
Of course, the film also has a more philosophical quality. Johnny Gray (Buster Keaton) is constantly fighting against the universe, no matter what is thrown against him. Like in a hamster running wheel, Gray is eternally running against the universe. In this one endearing young man, many of us can see ourselves, running against the universe, trying our best to keep riding the rails of life, even if life is deterministic.
Yet, I believe the film holds its quality in discussion rather than in viewing. Sadly, for me, the comedy has aged. There are so many times Keaton falling over can make me laugh. Undeniably, his acrobatics are impressive and the jokes are smirk worthy, even at times snickerable (yes, that is a word). But, I rarely laughed out aloud. One must remember, that is due to desensitization. I more akin to German Expressionistic cinema of the 20s, that avant-garde artistic era, and while I can certainly appreciate this and adore its values under the surface, it doesn't always work for me.