One of the funnest things about FPS games used to be using codes to unlock all weapons and ammo after beating the game. It was such a blast going through the early levels with these overpowered weapons you normally wouldn't get until near the end, just dominating every enemy you came across. Fun as hell in open world/sandbox games too, GTA 3/Vice City with all weapons, glorious.
Sad how things change. Or have they? Did the last GTA game have cheats? I actually haven't even attempted to find any for many of the games i've played this gen haha
Part of it is due to achievements and trophies, but another aspect, is the prevalence of "online mode" and "multiplayer" modes.
Though, there are a few (older) Xbox 360 games that still include cheat codes (there was a thread on Xbox360achievements.org that showed the games that allow cheats, and don't disable achievements), but I've not played any of them.
I'd like it if, even excluding cheat codes, there were more "New Game+" mode games on the market, allowing players to carry over the gear they unlocked during their first play through, and then have instant access to it in NG+, regardless of whether you have the correct stats for using it.
Not only would it give people more reason to replay the game (because who wouldn't want to rock end-game gear, at the start!), but maybe if you have a series of "New Game" modes (+, ++, +++, etc), where you can also ramp up difficulty, while maintaining your equipment from previous saves, it could add some fun and challenge to the game.
I think Dark Souls might be one of the only "current generation" games, I can think of, that has a system even remotely like that. I haven't played it, so I don't know how the DS "New Game+" modes work... but it's the closest thing I have to compare what I'd love to see, with what's currently available.