Kingdom Hearts II - Final Mix ^_^
Not only does KHII improve on everything that made KH1 great, but it adds a bucket load of new functions and goodies, has beautiful graphics that still hasn't aged for a game released in 2005, better controls, and I would be here all day if I were to list it all xD
And if that wasn't enough, Final Mix II adds even more extra content........... like............. what more can you ask for??? 8D
While not my favorite game, I did love KH2 and I'm looking forward to the hd release in December on PS3. The combat was phenomenal, especially compared to the rigid combat in the first game. KH2 took all the fluidity of a game like God of War and added it to an amazing world (plus, I could make Donald and Goofy disappear in order to make myself more powerful).
As far as number 1 game of all time...that's a tough one honestly. I know my top 5, and I'm sure no one will be surprised by the list (well, maybe one of them).
Final Fantasy VII
Final Fantasy X
Mass Effect 2
Mass Effect 3
The Last of Us
I imagine it is pretty unoriginal, but I would probably have to say Final Fantasy VII as my number 1. While FFX is a very close 2nd, I don't know if I'd be as avid a gamer as I am now if I hadn't experienced FFVII when I did. It is the reason I love gaming and rpgs. I'm not going to pretend its perfect, but it will always hold a special place to me.
That being said, I'd like to give honorable mention to the .hack franchise. <3 Definately in my top 5 franchises.