4. Bottomless Inventories
"How to defeat that boss? Easy! Let me look through 40 rocket launchers, 65 pistols, 30 shotguns and 180 SMG's to find what works best!" That basically describes a lot of today's games that lack the difficulty of having a limited arsenal. What's arguable in this reason is that, many games (like Borderlands) are designed around this system, but other games have no excuse. For all my love for everything Metal Gear, I can't help but think, where does Snake/Raiden hide 5 cardboard boxes, an RPG launcher, 3 assault rifles, etc etc? A neat mechanic in Uncharted and BioShock, for example, is the weapon limiting system. Your characters simply can't carry everything, and you have to make decisions on the run. Pick up the Grenade Launcher, in case you need it? Or stick with your M4 that has full ammo? What have I faced so far, and what are the chances I'll face something new soon? Remove the tactical layer and the lack of safety from the player, and you got people that can finish every such game given enough time, in big or small amounts.
Example: Metal Gear Solid