#5 Mario Kart: Double Dash (Gamecube)
My personal favorite in the Mario Kart series. Double Dash has an impressive variety of characters and racetracks. Like Mario Kart 64, it offers a reasonable challenge and isn't too frustrating...but its single outstanding feature is the ability to pair any two characters together for a chance to get either of their special weapons. My personal favorite pair is Mario with his triple fire balls and Bowser with his giant koopa shell.
#4 Super Mario 64 (Nintendo 64)
The game that set the standard for modern platformers; frequently imitated, but never truly recreated. SM64 is almost two decades old but hasn't been forgotten by anyone, especially by me. It is the first game that I completed 100%. The levels are a marvel, even to this day. They are all so creative and mysterious. The only thing that prevents this game from being any higher (lower) on my list is the camera, which can be very difficult to manage.
#3 Super Smash Bros. Brawl (Wii)
The strongest game in the Smash Bros series, so far. Brawl was the reason I (and countless others, I'm sure) got a Wii. It lacks the charming old-school atmosphere of the original Smash Bros but has even greater variety than Melee. It has some of the most exhilarating, stylized, and easy-to-master combat of any game I've ever played. It also has the most appealing visuals I've ever seen in a game; just the right mixture of realistic and cartoony art styles. It introduced plenty of beloved characters including the angelic Pit, the enigmatic Meta Knight, the sleek and sexy Zero Suit Samus, the Playstation veterin Solid Snake, and Sonic, the fastest thing on two legs.
#2 Donkey Kong Country 2 (Super Nintendo)
Nostalgia...atmosphere...those are what come to mind when I think of the DKC series. Donkey Kong Country 2 has almost everything that the original had and much more to offer. DK himself is absent in this game and so its Diddy's turn to shine, along with his invaluable new partner, Dixie. This game has much more threatening enemies, much more challenging bosses, and much more fantastic and at times nightmarish settings. You are responsible for getting the aspiring heroes safely through sunken ships, volcanoes, swamps, giant beehives, a treacherous roller-coaster, a floating bramble maze, and even a gothic castle.
#1 Kingdom Hearts and Kingdom Hearts II (PS2)
Those who know me surely saw this coming. Yes, I am totally in love with the Kingdom Hearts franchise, where the magic of the east and west come together. It has irresistible characters, music that is beyond epic, the most dynamic and fluid combat systems SQUARE has ever created (none of that turn-based crap), and a story like no other in existence! Both KH and KH2 are equally enjoyable games overall, neither too easy nor too hard. They also have just the right balance of SQUARE and Disney-focused stories. Two things that KH1 has that KH2 lacks are more impressive level designs and more challenging bosses. Two things KH2 has that KH1 lacks are more engaging space battles and more exciting combat.