The reason why Celeste is much more likeable and symphatetic than Sayaka

-Makoto was a saint. And you have to interact with him only for couple of hours to perfectly understand that.And he had a crush on Sayaka. And she even loved him back! -Leon was... Just a child. Seriously, just spent couple of FTE's with him and you will see how much innocent he actually is.And Sayaka is implied to know he is interested in her. -Ishimaru, at the point when he was killed, clearly was on the road of becoming an Ultimate Despair member.Possibly,if he wasn't killed, he would have commited murder of his own(possibly even accidentaly). -Hifumi was a pathetic virgin whose only goal seemed to get attention by any means. Celeste clearly didn't had any feelings for Hifumi.

That's pretty much it. No, I don't think that Taka or even Hifumi deserved to die. Yes, Celeste was evil when she tried to kill everyone by winning her trial. No, Sayaka really planned to murder a person and betray her friend in a cold blood. Yes, she really should have thought about a possibility of her friends already being dead and her murdering Leon for nothing. Also, she should have thought about angry Mondo lynching Makoto for "killing" Leon, for example.

Celeste is a sinner, but at least she is not a Judas. Sayaka is pretty much Judas.