Do you think Katherine became so fascinated with Stefan and Damon because they reminded her of Elijah and Klaus? And which Salvatore reminded her of which Original if that's the case?

maybe

Elijah and Stefan: Both were kind and lovely, both have so much love for their brother that they forgive them everything

Klaus and Damon: Selfish and impulsive

Maybe the reason why Katherine wasnt in love with Damon was because he remind her Klaus, and at some point he was like klaus, killing people, betray their friends etc

I don't think so... I think that Katherine had totally lost her humanity when she met the Salvatore brothers but her love for Stefan kind of brought it back. She was in love only with Klaus back then and she didn't even kiss Elijah (we don't know it yet at least) when she slept with Damon so many times. I think She was actually just playing and she found herself falling in love with Stefan. But it wasn't enough to make her choose someone else but herself.
Damon is definitely Elijah and Stefan is Klaus. I'm sorry for what i'm about to say but i really don't get why everyone says that Stefan is good and he's not evil like Klaus etc. Stefan is capable of doing bad things and he has proved so many many times. And as his past reveals he has been evil once and Damon tried to stop him. And Damon isn't evil. He is hurt and now he's in love with a woman that he can never have (i'm a fanatic DE supporter sorry..!). Just like Elijah was with Katherine.

Yeah, maybe.
But I think Damon reminded Katherine of Elijah because Damon used to be the boring one and Stefan reminded her of Klaus as he used to be the charming one. And after Katherine "died" then Damon and Stefan swapped roles.

I think Stefan reminds her of Elijah because she loved both of them because they were gentle, loyal etc.

Then Damon reminds her of Klaus because he was competive, rough and she liked the idea of having the control over him.

♥