Mainly their roles, personalities, powers. Saber has quite the dignity that I like and somehow I can relate to her personality, I suppose.
Yeah, fair enough.
Personally I can't, really. I dislike the concept of Chivalry (to me it was just an excuse for the powerful to ensure that the wars they caused would have as little effect as possible on them
, not to mention extremely sexist, especially the more modern concept of it) and I'm not too fond of Saber's overly-honourable and lawful nature, either. She seems to follow rules just because they're rules, and to me that is idiotic.
However, other people like her mainly because she is the most popular character out of Type-Moon.
I'm the opposite, honestly. A large part of why I dislike
Saber so much is because of her popularity, and how she always hogs the limelight and appears everywhere. Especially when Sakura is largely ignored.
Unfortunately though, her route is quite 'unfair', I was always expecting much more focus on her character back then.
What do you mean?
I thought her route focussed on her a reasonable amount, honestly. Not as much as HF does on Sakura, no, but more than UBW does on Rin. And, Saber does get some character development outside of Fate, too.
And I agree with that. Usually people like characters that are popular just because.
I find the opposite. If a character is popular they tend to be disliked
for that. Although, there is a certain hive-mind aspect that comes about sometimes, particularly with regards to attacking less-popular characters (Sakura on 4chan and various other places, for example).
The design also plays an important role. There are characters with a totally empty personality, yet they are able to become popular just by their design. Also, the anime plays an important role, mainstream popular anime tend to make their main characters popular enough.
I have seen people that never played x game for example and they like x character because he/she looks strong, has good looks, etc.
That seems like a bizarre reason to like a character, honestly, but I guess that people don't have to always justify it....