I think two identical people would not get along too well, as well as two people who are completely different. I would hate if someone had the exact same interests as I did, someone who was basically the exact same. We would get into so many arguments. For example, I am a bit stubborn, and my boyfriend (luckily) is not that stubborn, he's really laid back. I'm an organizational freak, I plan things super in advance, he is more spontaneous. Those things work well when we are opposites. Like, he lets me loosen up, be a bit more spontaneous. And I am able to plan things in advance for the both of us, stuff like that.
But I also think you need to be similar. For example, I'm hygienic, care about my looks, etc. My boyfriend is too. I'd hate someone who was dirty and never cared how they looked in public, etc. We have some similar interests (music, drugs, cooking, computers) and some different interests as well (he's into chemistry, research, music production, etc. while I'm into animals, baking, clothes, etc.). It evens out - we have enough similar interests but also some different interests, too, which keeps things balanced.
