Could never have a single favourite I don't think.
On the Amstrad CPC I remember Fruity Frank and Who Dares Wins II as my go to games. The others were good and would easily play them all again, but don't think I ever had more than about 6 or 7 games. I didn't ever seem to want others possibly because I was too young.
On the PC my favourite era was Doom II, Hexen, Heretic, Duke 3D, all very similar so there were always new maps and addons to play around with and quite often had ppl over for LAN gaming - never needed the internet, especially when Duke3D brought in the magic number 8.
On the SNES, Street Fighter II Turbo, Mario Kart, Super Mario World + the remastered versions of Mario 1, 2 and 3