I'd say both are always needed and the real problem lies in finding the perfect balance between the two. That being said the main focus should not be on skill or luck but on fun. In a multiplayer scenario you will always have whining coming from both ends , either a highly skilled pleyer gets a grenade thrown at him blindly which explodes right next to his head and starts pissing and moaning at the luck of the other person or a person with no skill whatsoever gets pissed because he can't move from point A to point A + 1cm without getting shot in the head by previously mentioned skilled player. The only real way of handling this imho is being very selective with who you want to play with to ensure that you get the experience out of the game that you want.
Then again , perhaps we should not call ourselves ( or others ) highly skilled if they cannot counter a piece of good luck from the opponent ( granted this is not always an option ).
Then again , perhaps we should not call ourselves ( or others ) highly skilled if they cannot counter a piece of good luck from the opponent ( granted this is not always an option ).