I don't think any game will ever topple Grim Fandango as the one I admire most. Call it a mixture of unbelievable quality and nostalgia, or whatever you like, but the end result is an experience that I never fail to get fuzzy just thinking about. Even replaying the game last year reminded me how its magic hasn't faded, and just how masterfully produced it is in every single way.
I mean, it takes a really special game to keep people talking about it this many years after its release, and with such passion. It's just one of those games that makes you want to.