Bruce Lee is still awesomely enjoyable. Terry's Big Adventure was a very good budget game. Lode Runner and Chuckie Egg are lovely simpler nonscrolling ones
I never could stand the early 'big boot is going up and down you must pass under it with pixel precision or else die' screen-flip ones. I guess Monty on the Run and possibly Trollie Wallie were okayish.
And Ghosts'n'Goblins is awesome but harder/more frustrating on C64 than on arcade for some reason. But an eternal classic.