For me, the movie was just very average but with the addition of a number of stars and high production values. I voted no as there's nothing that makes it stand out in terms of quality or influence, so it doesn't deserve to be in the canon.
The point about not being aware of many WWI movies was interesting to me as a Brit. For us, there have been so many films and books about it and I just subconsciously assumed that was the case for everyone. Thinking about it now, though, all of the WWI movies I've seen have been either British, European, Australian or Canadian. It's interesting to realise that an event which was of such huge significance for our history is something of an afterthought for the USA.
If anyone is looking for WWI movie recommendations, personally I'd suggest Regeneration. It's also a nineties movie and it deals with what was then called shellshock (now PTSD). It's mainly set in the real war hospital of Craiglockhart in Edinburgh with Siegfried Sassoon and Wilfred Owen as supporting characters.