I personally love OddxAelita and UlrichxYumi. I also really like JeremiexAelita, WilliamxAelita, UlrichxAelita, WilliamxSissi, UlrichxSissi, and WilliamxYumi. I think JeremiexYumi is kind of awkward, same for OddxYumi and OddxSissi. But I think JeremiexSissi would make the WORST couple ever because they absolutely hate each other and have nothing in common. Hehe, sorry for the bias.

I don't like jeremie and aelita as couple they are not perfect together. Odd and aelita are perfect together, not jeremie and aelita. Odd and aelita are the greatest couple ever.

How can you not like yumi and Ulrich together

Well I cant like them together. First Ulrich played Mindgames with Yumi, Second he gets jealous everytime he sees her with any random guy, William or even Kiwi, when he startes too long at her. Third, he treated her sometimes like crap. Fourth, when William adviced him to go to Yumi and talk from his heart, he refused it.
So there are four reasons. + I like guys who treat their crushes, girlfriends, whatever with respect, like William did.