I don't consider myself a fan of GTA4, but I have sunk a LOT of time into its multiplayer. The multiplayer in RDR is horribly unbalanced, and it doesn't have any interesting game-modes. Not to mention they held back most of the content for DLC.
GTA4 has many diverse game-modes, and you can choose to have the battle take place anywhere in the city. My favourite was cops 'n crooks. My friends and I had that down to a science. I'll never forget one of our victories. It was a highlight of my gaming career:
We joined a game of cops 'n crooks, and the lobby was full when the game began. One of my friends was the boss, so we were in control of our team. We told our team the plan as we gathered weapons and vehicles. I set the waypoint for the hotel on the southern end of central park. The plan was to have the boss take cover in there, so he can be easily protected, while I get the helicopter.
We raced to the hotel from the construction site in southern Algonquin, police in hot pursuit most of the way. We get to the hotel, and the boss takes cover in the elevator shaft, while the rest of the team covers the only entrance. My time to shine. Police are determined to get to the boss, but are caught off guard when I run outside. I kill 3 of them with head-shots, and make a getaway in a nearby car. Since I'm not the boss, none of the cops decided to follow me.
I get to the chopper, and tell the boss to get ready to move. Once I'm hovering above the hotel entrance, I could see the cop team still trying to reach the boss. Once my team knew I was in position, they erupted from the hotel. With all of the cops dead, I landed. "The boss has reached the escape vehicle!" I took off, turned a corner into time square, and waited for the scoreboard to appear.
I really wish we recorded that. Anyway, GTA4 is much better than RDR. Why didn't they have a similar game-mode? It could have included bank/train robbing! One team can ride the train, escorting an important shipment of some kind, while the other team tries to stop it. Why didn't Undead Nightmare add a game-mode inspired by L4D? Fight your way from Escalera to Blackwater, and board a ship out of there. The zombies could get worse at night, forcing you to hold out in a settlement. That would have been amazing.