I can't really decide between Age of Empires II or Battlefield 3, but I'll use Battlefield 3.
It was rushed out ahead of schedule so it was riddled with bugs and balance issues from the start, the hit detection is just depressing at times, the singleplayer campaign is the worst I've ever played...*Deep breath*...The co-op campaign was too short, had no vehicle sections apart from one in a helicopter, a lot of the maps in multiplayer are too cramped for 64 players, which is the mainstay of Battlefield, there's no Commander mode, some maps are really unbalanced in terms of advantage for one team...
Etc.
It was rushed out ahead of schedule so it was riddled with bugs and balance issues from the start, the hit detection is just depressing at times, the singleplayer campaign is the worst I've ever played...*Deep breath*...The co-op campaign was too short, had no vehicle sections apart from one in a helicopter, a lot of the maps in multiplayer are too cramped for 64 players, which is the mainstay of Battlefield, there's no Commander mode, some maps are really unbalanced in terms of advantage for one team...
Etc.