Metal Gear Solid 2 improved on every single aspect of the original. The ability to actually shoot from behind cover, the implementation of walking/running, a first-person aiming mechanic that the original sorely lacked(most likely due to technical limitations of the hardware), holding up guards, shooting out radios, the ability to go through the whole game without killing anyone, collecting dog tags etc. I could go on and on.
Perfect Dark took everything that made Goldeneye amazing and amplified it. Better graphics, more weapons, alternate firing modes on every single weapon(even melee), more complex and involved missions, more intricate levels, feature packed multiplayer, AI controlled bots, counter-operative mode, co-operative mode, certain levels from Goldeneye included for multiplayer, smarter enemies who would call for back up and/or pull out pistols when you disarmed them. Amazing.
Killzone 2 massively improved on the original, as did Gran Turismo 2 and GTA3.
Ocarina of Time/Super Mario 64 deserve huge mentions if they are considered true 'sequels' to their SNES predecessors as both were hugely revolutionary.







