Here are my favorite games:
Robopon(GBC):
My first game ever. Sadly, I traded it away for a couple Poke'mon cards back in the day...<img src="smileys/smiley19.gif" border="0" align="middle" />
Animal Crossing(GCN):
My cousin introduced me to this game when it first came out and we played it for days on end. We watched eachother play and waited for our turn. I loved the anticipation, and the competition we set for one another(who could pay their house off the first).
LoZ: Windwaker(GCN):
This game was is still my favorite game ever. I loved the cell-shading and the puzzle solving. The story was excellent and the sailing and adventuring was very fun; you never knew what you would find next! Of course, I was extremely happy when I beat a particular part of the game(I was young, after all, lol). I did have to get a guide to beat the game though.
Poke'mon Gold/Silver(GBC):
These games were the pinnacle of my childhood. I spent hundreds of hours playing them both(even though they were the same). They were the best Poke'mon games ever, IMO. They remind me of happier times, and I still play them every now and then.
Alice: Madness Returns(PC):
This came out just recently. I always loved the theme of playing a character who was in an asylum(the psychotic aspect was interesting to me on how it affected the gameplay). Plus, it was the first game in a long time to actually disturb me(I won't spoil anything, but chapter 2 freaked me out for some reason). The amount of detail is excellent and you get the first Alice for free.
Of course, Super Mario Sunshine, Luigi's Mansion, the GTA series and many more contribute to my favorites, but I picked the ones I had a lot of memories with(except Alice). <img src="smileys/smiley1.gif" border="0" align="middle" />