Fallen Warrior Makina is surely one of the best looking CGs out there. The art quality is hella good and one I thing I like is that her body proportions are like always the same from different angles and such (which is good)
Funny thing, Princess Go Round is at my top "hottest CGs" too but I find it too bad that the corruption is wayy too sudden in that game. I would've enjoyed a lot more if things went a bit slower.
Mature Quest, oh boy. I remind trying to actually play that game, just to find myself gettin a 100% save file and then saving the game folder in my HDD for months and months to come. Also, too bad they didnt make a sequel or something.
My personal favorites are a couple of games of 'shinachiku castella' and 'Tengsten" circles. Tina the Scarlet Swordsman and Ane Kasegi. If I had to choose artstyle (aka protagonist looks) wise I'd pick Ane Kasegi over Tina, but CG wise Tina>Ane. Overall, shinachiku castella remains one of my favorites circles of all time. It has all my fav tags and good artstyle as well.
(Yea my english is garbage, sorry about that)