As I've said before. Contra is just about learning. I can finish it without losing one life twice in the same row using the same combination of keys.
Level 1 : Go forward till you see the first soldier shoot twice, killing him and the one behind him, another bullet after 5 steps to kill the third soldier. Let the weapon capsule get just past you and then jump shoot diagonally down forward. Getting it start jumping repeatedly while crossing the bridge. When you reach the other side keep shooting fast like a maniac , and when the weapon capsule reaches you shoot twice, the first makes you get the S-weapon the other kills another soldier
Keep going forward while on the top level till you face an automatic gun, jump and shoot diagonally down forward. Keep moving till another two weapon capsules appear just go and jump to the next side while shooting the upper one (The other one contained Laser which isn't as important as S weapon) . Still in air you can shoot that guy trying to kill you. jump till you reach the last island, killing another soldier when you are doing that last jump. Go down after the first cannon, just ignore it but shoot fast the second one. The level boss is so easy now as you have strengthen your weapon, just shoot his weak point for 2/4 seconds maximum .
All the levels have another key combinations :sarcastic: . If you really want a hard Platformer choose :
Metal slug 3
Shock troopers 2
Mega man 1
Super Mario the lost levels
Contra 3 : the alien wars
Castlevania V (not as hard as the others though)