If there is one thing that improves a Single Player campaign for me is being allowed to play it with a friend. Saints Row 3 basically has made Grand Theft Auto irrelevant to me and hearing GTA 5 doesn't have this feature either, I'm more excited for a Saints Row 4 tbh. It just adds so much more fun being able to play the main game with a friend. Gears of War was so boring when I played it, however being able to play along side a friend actually made it enjoyable and I'd put it as one of my fave games of all time. Now the game wasn't that great, however just the experiences I had with my friend in the game made it such a memorable game for me.
Now not all games need it, I just wish'd more that suited it would do it, like GTA 5. If you're going to have 3 main characters, why couldn't you have made at least two playable at a time? It would have been fun to be in this city causing chaos with a friend with the full content of the main game. It's not fun being in the city with no content and it just being like a Death Match.
I just want this to become more of a standard feature in games, it's much more fun to play with friends than alone. In real life you never play games on your own when you were growing up, you were always with friends playing them. I mean take Sim City, what could make it more fun? Being able to just create a city or rival cities with your friends. It would be like when you play minecraft and you're just building a base together, it's fun to see each others ideas. So I'm happy that they're doing this online thing for Sim City if it plays out that way, though knowing EA it probably wont, it'll just be there for always online DRM and to charge us £400 for DLC like The Sims.
Like trying Crysis 2 today, it's such a boring game, It's another one of those generic Crytek games where they seem to have no artists or writer involved to actually make you like anything. Shove coop play in there and it could actually be fun going through the levels with a friend.