The best ones I've played so far (all hentai games obviously) is:
School Days <<< completely animated, it was 8 gigs when i dled it X_X
Summer Days <<< completely animated, 6 gigs x_X
SHUFFLE! <<< just for Kaede
, stay away from primula ;oAIR <<< good story and music
Metamor Fantasy <<< also has a RPG style battle aside from dating
Fate Stay Night <<< lots of alternate endings, one wrong choice.. you're dead
Kimi Ga Nozomu Eien <<< good story and HOT scenes ;p
I played them all in Japanese XD
oohhh im such a perv.. ~o~