There is a lot good 2D games but im looking for 3D game with "realistic graphic" Unfortunately there is only 3 things that i like in House party. "Realistic graphic", npcs seem to be more "alive" (for me at least) and you can start scene basically everywhere in any time. In other game you start scene in specific circumstances and you are "cut off from rest of the world".I'm afraid not. House Party is actually quite unique.
No one else dares to create games in a 3D environment (with very few Exceptions like Bonetown, The Last Barbarian and The Vikings Daughter)
You might however find some 2D zelda style games with moving characters.
Last Hope is very good game, but npcs have very strict schedule. You start scene in specific circumstances, not whenever and wherever you like.You could try out Last Hope, its not as in-depth or free willed. But you can move around freely and interact some with NPCs and environments.
From what i remember AI Shoujo npcs don't have specific schedule but you are "cut off from rest of the world" during scene.NPC follow strictly their schedule in Last Hope. House Party doesn't have a proper schedule because it happens in an evening only and most of NPC wandering are random.
Artificial Girl 3 from Illusion had a mixed approach with girls that follow a schedule but also do random actions and can even begin sexual interactions.