If Vocaloid was an anime, that would be my choice, but since it's a computer software with anime styled videos and characters, that probably doesn't count.
Otherwise...
Hetalia - I dunno. I just would want to be able to have literally LIVED in World History.
Sailor Moon - For the same reason Caroline stated a few posts above me
Shugo Chara - I dunno how to explain this one in words. The concept of it just is really fun.
Might list more when I can remember them...