Where do I begin in answering, with the first question that is:
1: Given a chance to create an anime-cartoon crossover I would make it a DBZ and Justice League Unlimited crossover, oh yah.
2:Can onslaught beat Goku?
Yes he could becuse the dude can destroy a universe.
3:scarlet witch vs. witch hunter robin?
Scarlet Witch because did you read house of M, the lady change the entire Marvel universe with her chaos magic into what her dark instnicts made her believe it could be. The lady is hot and volitie, I like it.
4:superman vs. goku vs. thor?
Good one, but Goku wins this for one Sups' looses first because unlike the other two he doesn't have any fighting techniques or disciplines. While Thor would loose because he can only be pulled by his hammer, he can't fly and all Goku has to do is loose the first round, come back an hour later and he's about three times stronger than he was the first time they fought. Goku takes this match.
5:pikachu vs. bugs vs. mojacko????
I have no idea
6:would kenshin fall for jean grey or maybe for wonder woman???
Jean Grey is nuts, she'd kill him before he had a chance to ask her out, and hell yah he'd fall for Wonder Woman what straight man wouldn't.
7:evil eye (mido ban, getbackers) vs. sharingan vs. optic blast vs. byakkugan (did I spelled it correctly??)
Optic blast wins every time.
8:can marvin the martian catch the silver surfer???
maybe?
9:can quicksilver tame tazmania???
Hell no know one can, except Wonder Woman.
10:will midori fall in love with frank(xavier's son)?
Yah?
11: who's the better mouse, mickey or pikachu?????
you sure pika,pika, is a mouse? the coolest is pika because that is what I call my sister's cat, they look just alike.
12:any wierd love team???
Love team, maybe Batman (Bruce Wayne) and Major Motoko Kusanagi (Ghost in the Shell). They both have a very dry, dark, and secluded essence about them, perfect match.
Peace.