Errr... excuse me, but it is very,very easy to get a maximum score in Turrican II
In Level 1-1 when you move to the right until the point where you must jump up the mountainrocks, you find a nest with killer-bees constantly flying out. Unlimited killer-bees will appear until you destroy the nest.
Now grab your joystick, move your joystick to create a 45 degrees angle electric beam, hold down the firebutton with some ductape, get some coffee, do some shopping and return 2 or 3 hours later. Et voila: you have earned a mega highscore (unless you score higher than 9,999,999; the counter will then reset to zero
A better challenge would be declaring the one with most time and lives left and having the highest score the winner.