You can't judge a relationship from the outside, or why Scott Pilgrim must end up with Ramona FlowersThis post will be spoilerific, both for the comics and the film. Indeed, the title actually is, but I like it so much that it stays.
[Before I begin, an aside. I adore Scott Pilgrim, I think its a splendidly inventive and funny film that never fails to entertain. Its just visually lovely, and it brings many elements of the comic to life in a very profound way: I love the way music is portrayed throughout the film. That said, theres no doubt that the central romance is flawed. I am going to argue that Scott must be with Ramona, but the film fails to sell that. Apparently the original ending was to have Scott end up with Knives, which explains, perhaps, why the film is a bit tonally strange in this regard, with lines that make little sense in the final version. The films biggest crime is its portrayal of Ramona, who is, in the comics, clearly very into Scott. I actually blame a lot of this on Mary Elizabeth Winstead. In the comics the lines she speak come across as affectionate and wry, but in the films they come across as a little dispassionate. Even in the scene where Ramona fights for Scott, she seems mostly annoyed rather than interested in Scott. This does undersell the ending, something the comics definitely do not do.
Nonetheless, the film supports Scott's relationship with Ramona far more, and is an excellent example for what I'm about to say, so I'm going to go ahead and say it. I just wanted to make clear that I was aware of the flaw in my own argument]
So, some people, who will remain nameless, believe that Scott should get with Knives at the end of the film. Indeed, Edgar Wright thought so as well, his thinking being informed by just having read Scott Pilgrim Vol 2. Its certainly true that theres some parts of the film that reinforce this idea, and Knives is very much into Scott. They work together well towards the conclusion of the film.
But heres the thing Scott isn't into Knives. I'm sure everyone has known friends that they think should be together, but aren't, because theres not a mutual attraction. When you get down to it relationships need that mutual attraction. Not to mention of course that Scott has been a dick to Knives throughout the film, so has hardly proved himself worthy of her. She IS far too cool for him.
People need to be in the same place mentally for a real relationship of equals to work, and Scott and Ramona have that- they both have baggage from past relationships weighing them down, and the emotional maturity that comes with that. Knives has none of that, making Scott distant from Knives automatically.
Its very easy to view a relationship from its exterior and not understand how it works. One makes the assumption that how the couple are individually is how they are with each other, and thus head to erroneous assumptions. You don't fully know people, because you don't get to see how they're like in every situation.