Kingdom Hearts Birth by Sleep. The only thing wrong with the game is how empty the worlds are and how short it is. Then again it was a PSP game. So I imagine Kingdom Hearts 3 (Whenever it comes out) will probably be the perfect Kingdom Hearts game and thus my perfect game. The awesome combat system, longer overall game with more things in it, the awesome story and characters, and I dunno multiplayer where 3 or maybe more players team up and fight hordes of enemies.
Rune Factory Tides of Destiny, Skyrim, Persona, Romance of the Three Kingdoms 8 and the Mass Effect Trilogy. Wow if all my favorite ideas from those games were put into one game with a infinite budget... ohhhhhhhhh perfection.
The 2 recent Fallout games are really close. If they combined a few of the life-sim aspects from something like Fable, I would pretty much never leave them.
Open world Bethesda type games in general, with all the exploration & immense worlds, tend to draw me in the most. However, I would like something with a better combat system, with actually different fighting styles for different weapons.
So basically: New Vegas + life-sim (ala Fable 2) + variable but smooth melee combat (ala Kingdoms of Amalur).