Individual games?
5: The Elder Scrolls 3: Morrowind - A living island is your playground, but not in the GTA manner where you can just kill with no huge consequences. This game is tough due to its gameplay model, but once you play long enough to know how to enchant a Restore Fatigue shirt or amulet, you'll feel so rewarded. This is a game that encourages exploration and survival, on top of having one of the most unique settings I've ever seen in an RPG.
4: Yakuza 2 - This game has my favorite gameplay model, short of the Zelda games, of all time. A smallish chunk of city, but my God if it isn't a living, breathing chunk of city. You can explore the city in a more intimate way than the big sandboxes, letting you enter goofy shops, talk to random people, and get into brawls. Tells an awesome story full of badass moments, has sidequests and minigames out the ass and around the corner, and a sweet fighting system to put it all together. One of the most complete games I'm STILL playing.
3: Killer7 - This game is so fucking amazing. It's the most effective simulation of what it's like to enter the mind of an insane person and see how he views conflicts and geopolitics. Oozed style, had the perfect gameplay for its fantastically out-there story, creepy visuals, phenomenal music...awesome adventure.
2: The Legend of Zelda: Ocarina of Time - The game that got me into videogames. Not much more needs to be said about that, but I'll try. This game consumed my life as a child; this game taught me English, seeped into my dreams, and just would not let go. When I beat it, I fell into a two-week long depressive state where I had no idea what else to do with my life.
But if my #2 made me as a gamer and inspired nostalgia...
1: The Legend of Zelda: Majora's Mask - ...my #1 game of all time deconstructed the legend and infused it with an unprecedented amount of maturity that holds up even today. MM and OoT are honestly a hair's width apart on this list, but I give the edge to Majora's Mask for having created the most convincing apocalypse scenario I've ever seen in gaming, and it did it entirely out of fantastical elements. I cared for every NPC, I wanted to make them happy. Knowing I couldn't gave the story such an edge...and so unintentionally, as the main point of the 3-days cycle was just to conserve processing power...but holy crap, it worked so many wonders for the story. My best game of all time.