Imagine someone trying to compare the sims 3 modded to CM3D2, that'd be silly right? But that's just how different the games are. Koikatsu is similar and often compared to AA2 but is nothing like AA2 at all at heart, Modded Sims games are closer to aa2 than Koikatsu. It can make pretty girls but so can 3d custom maid, honey select was also a studio game, the new Ai Shoujo hasnt won over anyone, play home didnt win over honey select fans, so ultimately by comparison AA2 will look like the best because it tried to be something more. Koikatsu is a poser game, the gameplay is a self insert Visual Novel while the real meat lies in the studio. The modifiable character creator on top of that produces great results, and each character has personalities, traits, and sometimes modules if you dip your toes into the modding community, of which is the best way to play this game these days. many people will accuse the game of being shallow but are only ever familiar with the vanilla gameplay rather than the expanded modding community.
Click to expand.aa2 laid the foundation for other modders to edit the game to their liking.