Topic: When does an OP player ruin a game?

[Crying Freeman]

A complaint I hear a lot from players and critics; sometimes the player can be OP, making the game too easy. Mostly hear this about modern day games, but also CV4 and SOTN. I can agree that a game can be boring or numbing if it's too easy, but there are some games that are still great when easy (Unreal Tournament SP, CoD SP on easy, and the two CV games above). It is technically bad design to make an OP player(something that I admit despite the fact it could kill my argument below), but lets dig deeper:

Player OP due to:
Default mechanics/abilities:
A player with TONS of health, not enough health taken when hit, very powerful, long reach etc.

After gaining power-ups or weapons:
Pretty self explanatory; pick up a power that gives you too much health, makes your damage greater against enemies, getting a longer reach etc.

CV4 falls under the first category, SOTN the later. In CV4, we all know Simon can whip in 8 directions, the enemies don't hurt too much. SOTN, once you get the right weapon like the crissaegrim, bat or unlimited mist, falls under the later. I can see the complaint with CV4 because the game gives you that power by default (granted you pick up power ups to get the better whips, but once you get a better whip, you're stuck with it until you die, and even if you purposely try not to pick up a powerup, you're very likely to get one accidentally). I don't understand with SOTN simply because you can choose whether or not you want to use the weapons or abilities you have.

You get the items I mentioned above from SOTN, you can bypass pretty much every obstacle no problem, but can it be an appropriate complaint if it's entirely optional for the player to use them? I recently watched Mike Matei's review of MM9, and he mentioned how the metal shot makes MM2 too easy, praising the balancing in MM9 as superior. I didn't understand that because he isn't forced to use the metal shot, and he can turn it off any time he wants, yet he still chooses to uses despite the fact he knows it makes the game way easier.

Sure, an OP weapon in a MP game is different because you're against other players and it's a competition. But I never understood it in most SP games. If it's optional in the vein of SOTN, where you can switch powers or weapons, I don't see it as a problem since it's entirely optional, but in a linear game like CV4 where it's a chore to keep yourself form the OP abilities, I can see the issue there. I love games like Ninja Gaiden NES or CV1 where the player and enemy balance is perfect due to the abilities and limitations of both the players and enemies, but if I player SOTN and use an item or weapon that I know makes the game easier and unbalanced, I don't see why it should be counted against the game.