ZX81: I remember 3D Monster Maze and some Star Trek game with fondness... have u got those? How blown away I was at the time, man....
ZX Spectrum 48k: Manic Miner, JSW, Wally games(Automania, Pyjamarama), Dragontorc, Sabre Wulf, Atic Attac, Underwurlde, Knight Lore, Football Manager... remember FAIRLIGHT? Where the hell is that 3-channel sound coming from!!??
Blocky graphics were a critisism of the C64 for sure, but when you got Impossible Mission, Parallax, Uridium, Bubble Bobble and loads of other classics that escape me... who cared?
It's a bit old-fartish, but I dont't care - they simply do NOT make 'em like they used to!