I've played WAY TOO many to categorize them into TOP 10...
But lemme see.
01. Evenicle (Simply because it was my first proper H-Game [The one with story and allat]), also this was the game that ultimately made me learn Japanese
02. this is unfair, but... All of the Rance Series, I cannot in my right mind put these games separately because they'd take the rest of the leaderboard.
03. Lessons in Love (even though it has been recently falling out of me)
04. Eiyuu Senki series (made me love history)
05. The Last Sovereign - Genuinely made me respect older people, a calmer demeanor, and planning
---------------- From here, the games are in no particular order -------------------------
06. Masters of Raana
07. Ravager - Made me appreciate non-humanoid games, which in turn made me more open-minded and opened me various options in games
08. Headpats & Handholding - My first futa protagonist game, which also was wholesome, making me more open minded towards playing futa protags, and well... not limiting myself only to male protag (I am actually unsure if I played this or Ravager first, but both of these made me less biased towards only playing Male Protagonist games)
Insomnimaniac Games
09. My Mysterious Rule - Made me comfortable playing as an ugly bastard and gave me newfound appreciation for the genre
10. SUPERHUMAN - Excellent story and lore, truly captivating. Also made me... wouldn't say appreciate, but tolerate overly-proportiate body parts
Also, probably every single game AliceSoft made would rank really high, especially the ones TADA was in charge of.
I still have not found a game that made me appreciate tentacles and netorare/netorase. Which are honestly the last 2 fetishes with which games I am unable to play.