Brutus believes Caesar has become to ambitious and his excess power makes him a danger to Rome. He bears no personal animosity for him but feels he must die for the good of Rome
Cassius has a personal dislike toward Caesar. He too believes Caesar is too ambitious, but his main reason for wanting him killed off is a personal one. He feels Caesar has never given him the respect he deserves and resents him for acting like a God when he's in reality a man like everyone else.
Caius Ligarius dislikes Caesar because Caesar repremanded him for paying tribute to Pompey.
Metellus Cimber grudges Caeser for banishing his brother Publius Cimber for a reason unspecified.
The play doesn't give specific reasons for the others, but one can assume it's because they feel he is too ambitious. However, whether their motives are more for the good of Rome or for personal advancement is unstated.