There's so many video game sequels that I love... so I'll just leave it to sequels who (imo of course 
) surpassed the original:
Fire Emblem: Radiant Dawn: Radiant Dawn both improves upon its direct predecessor, Path of Radiance, and all other Fire Emblems before it. In my eyes, it is still the Fire Emblem to beat.
Resident Evil 4: While the original Resident Evil/REmake is an amazing game that deserves every ounce of praise it gets, Resident Evil 4 was truly a game changer. Far superior controls and a much beefier and engaging adventure made this one of the greatest games of all time.
Super Smash Bros. Melee/Brawl: Each of these games are amazing, and despite how much fun the original is, Melee and [especially] Brawl up the ante quite a bit.
Pokemon Gold/Silver & Black/White: Both of these Pokemon sequels get my seal of approval because of the "newness" they present the player with. In Gold/Silver, it was your first time out of the Kanto region, and everything seemed so grand and expansive. In Black/White, you never encountered a single old Pokemon during your initial 40 hours playing the game. Both were immensley fresh while still staying true to their roots.
Sonic the Hedgehog 2/Sonic & Knuckles: Both of these games are among my favorite of all time, and each improves itself over its predecessor, the original Sonic the Hedgehog. Sonic 2 introduced the Sonic Spin (crucial), Tails the Fox, and an awesome bonus stage. Sonic & Knuckles (and by virtue Sonic 3) introduced elemental shields (Electric Shields for the win!) and Lock-On Technology.
WarCraft III: Reign of Chaos/The Frozen Throne: Heroes, a much more engaging single player, and an incredible online community made WarCraft III my favorite RTS game ever. It still hasn't been topped in my humble view. Hopefully World of WarCraft can crash and burn so they can get to work on WarCraft IV.
Donkey Kong Country 2: Diddy's Kong Quest: Dixie Kong. 'Nuff said.
Paper Mario: The Thousand Year Door: A more robust world, awesome partners (Love ya Vivian!), awesome humor, and a better shine of polish made the second Paper Mario one of my favorite RPGs.
Castlevania: Order of Ecclesia: I love all of the Iga-vania's... but what sets Order of Eccesia apart from the pack is the protagonist Shanoa. *le sigh*
Super Scribblenauts: Adjectives!!! Oh, and far superior character movement didn't hurt either.
Super Mario Galaxy 2: How could you possibly improve on the incredible Super Mario Galaxy? Make a sequel of course!
Sonic Colors: Sonic finally broke the Sonic Cycle barrier wth this one. *Salutes*
Super Mario Land 2: 6 Golden Coins: The first Super Mario Land, with its very un-Mario-like physics (they can drive me crazy!) and exploding turtle shells, is quite the oddity. Thankfully we got a return to Mario form in the sequel.
The Legend of Zelda: Skyward Sword: As amazing as Wind Waker and Twilight Princess are (and they are amazing), there's no going back after Skyward Sword. Kew kew kew...
