My opinion on multiplayer coop is that even when a game is extremely bad having the game be cooperative makes the experience a lot more fun. This is a big statement and I think that it differentiates the people who play games and the people who develop them. There is a certain level of quality control that is just glanced over when people are goofing around. Coop inherently makes people be more involved with each other than the game itself.
Games like Diablo 3 on console accomplish this. The game is enjoyable on its own, but is only increased in fun by playing along with friends. Games like Saints Row 4 kind of hit a weird spot with this, for example the game is made for one player and the cut scenes play for one player. However, the game supports two players which causes there to sometimes be glitches and other issues with these clips. Though many of those become overlooked by the fact that you are playing with a friend because it is that enjoyable.
I think that the best examples of this genre are ones that are strictly multiplayer. They are the ones like Trine that give an experience that is only matched if you have multiple people. Sure there’s a work around it, but like the Lego games its showing you that multiplayer is front and center. I think that these are the best example because they focused on making games that were multiplayer and not shoehorning it in.
Sonic Boom is a good example of the opposite by making the game “split screen” to the gamepad lowering the already terrible frames and graphics even lower. This is a situation of too much of an attempt to force the impossible. It makes an already bad experience even worse. The biggest way that multiplayer can ruin a game is by limiting or lowering quality to the players by entering that mode.
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