He's more of a badass cocky guy and that works well as a lead guy (especially in this kind of gruop) better than the sensitive guy that gets depressed when his girlfriend dies. Plus, I think Wolverine is actually more in love with Jean Grey, it's just more repressed because Scott was in the way kind of. I thought X3 made this decently clear.

I read very few of he comics and only saw some of the show as a younger person, so I took the movies as something more stand-alone using the comics as a reference instead of a guide. I think these movies are better than most other big comic book adaptions (Spiderman, Fantastic 4, The Hulk) and it's because they don't stick to the comics so closely, they make their own identity. I don't think disregarding the source completely is a good idea, but making a new story is moe interesting to me.