GTAIV, just so you know.
Okay, what can they learn from GTA4:
- Cell phones ringing every 4 seconds with manditory requests from your 'friends' to go waste your time with bullshit or else losing rep with them is a terribly annoying thing
- A game running around doing people's bitchwork for the entire game is equally unfun and unriviting
- Niko cannot put on seatbelts and flies through the windshield every time you screw up and bump anything. That also is a pain in the ass
- A game that gives less customization than the game before it is also a pain (woops, actually this applies to both series. Though more on GTA4's)
- The ability to walk circles around a person and keep them just awkwardly falling to the ground is hallarious, but retarded
- A game that takes itself seriously is crap. At least overly seriously
- A game that takes everything its predecessor did and does basically all of it worse - Size of the sandbox, variety of sandbox, 2 player simulatious play (no, not everyone wants to pay for Live or can run that horribly unoptimized game on their PC), story, characters, side missions, customization, radio (Lazlo was painfully unfunny in 4. dont know why. Always loved him before), variety of vehicles, types of vehicles (planes!), and pretty much everything but graphics and physics engine, is similarly disappointing and unfun
so, the main thing to learn from GTA4? Make a game that's fun, and doesnt feel like a chore (CUUUZZIIIIN! WANT TO GO BOWLING!? NO!? I HATE YOU!)
And while we're talking about Rockstar, lets look at their other game: Red Dead Redemption
now, this game's single player was freaking awesome, no two ways about it.
But its multiplayer?
Take out almost all interiors, all stores, most NPCs, and make it either a world where nothing is happening (No-kill mode) or a world where people just sit around and snipe you over and over and over (either other mode, though one actually requires them to AIM).
That kind of multiplayer is crap. At least for any period of time. So they could take away the lesson of: FOR THE LOVE OF GOD KEEP FOCUSING ON COOP MODE!