Jazz Jackrabbit and Jazz Jackrabbit 2. Having the 2 original CD's in my hands right now. It happends I play these two games nowadays. Found copies that run smoothly under win7 x64 (Not original)
Emulators and the good old SNES are great. Super Mario World, Super Metroid, Super Battletank, hell... everything is super with the SNES!!!
No but seriously, even the NES has great games, the Mario games, Contra, Double Dragon, the Megaman series. It's all about quality, not age.
One of my old favorites was MechWarrior 3. It seems I spent more time modifying the Mechs than in actual gameplay, but it was a good gaming experience nonetheless.
Before for there was Advance Wars, there was Military Madness/Nectaris (TurboGrafx/PCE.) I still have my copy and play it every now and then. Good times .
Frogger, Boulder Dash, PitstopII, Summer Games, Raid Over Moscow , Spy versus Spy, Elite, Loom, Millenium 2.2 , Vermeer....