>Sakura
Overall sexiest body but completely brought down by her character (and more precisely, voice)
>Saber
My personal favorite, there's something about her character that makes her very attractive especially if you imagine breaking her in bed, also imo her second h-scene is the hottest.
>Rin
Amazing ass and legs, worst h-scene unless you count Rider's wet dream, great character - overall solid package and TM know this and went further with her with Isthar/Eresh.
>Rider
Amazing body. Overall kind of whatever in terms of character, done completely dirty by the plot aside from HF.
>Caster
Meh, she's too much into Soichiro plot-wise.
>Taiga
Also meh, she's Shirou's sister but her hijinx do not ever make her hot in my eyes. The Jaguar Man has nice tits though so could be good for paizuri in a pinch.

Ilya's mom is also stacked but she's a cup and also would be a bit annoying, plus she's paired with Kiritsugu and gets done in by Kotomine so whatever. Amazing body tho.

Overall (if we take everything into account) it's
Saber > Rin > Rider > Sakura > everyone else, but at the same time I think even Sakura is A tier.