Guardian (CD32) - Awesomely playable and a non-stop adrenaline inducer. An excellent example of the sort of video game I like best: quickly accessible, lots of action, zestful presentation. Retired many CD32 pads.
SWOS – Totally blew me away from day one. The greatest football game engine ever was (brilliantly) improved upon, and the added managerial elements and huge player/team database created a sense of total freedom in which to explore Planet Football. Retired countless joysticks.
The first few Amiga games I ever saw in action, on an A500, also impressed me greatly at the time: Lotus, Speedball 2, Lemmings, even Bart vs The Space Mutants, with its animated intro sequence.