Lost Planet 1 = Halo + Japan
Lost Planet 2 = L4D2 + Halo + Japan
If you'd consider L4D2 singleplayer, then get Lost Planet 2 single player. If you have a friend, just buy him a copy or play splitscreen (can't go splitscreen online). This game is designed around the coop, and has a decent coop multiplayer lobby, and fun mechanics. Easy respawns if you have 1 other dude with you.
I played through the whole game on Easy with 4 dudes. It's a blast. My one complaint is the multiplayer matchmaking. I can't figure out how to play easily with friends online. You can make a private room, or you can join a public room and try to get friends to join it too before it fills. You can't party up and then matchmake into public ctf games. Note: you CAN do this for coop, just not for ctf/competative modes.