That web-based Zombie MMO you were talking about earlier is
Urban Dead and it's pretty addicting.
As for Left 4 Dead 3... I dunno, I wouldn't mess with it too much. I like that it's different than most games in the genre and I don't think making it more "survival-ly" is going to make it better. It's a fast paced action game in a genre full of slow, plodding marathons and I think it helps it stand out. However, what I WOULD add/change is...
- Melee weapon destructibility. Melee is over powered currently, which is one of the reasons they took away the safe house bats for the pre-orderers. Making it so most (maybe not all) weapons ether break or become less effective over time would encourage people to change it up more often. Maybe make finding an ammo repair them too, if you REALLY want to stick with something.
- Make Adrenaline over-heal you if your at/near max health, but it make it wear off over time still. In fact, make it so that the Adrenaline health is used up LAST, so you might drop to the ground if your not careful. It'll make Adrenaline more effective, but also add in a drawback to using it. Maybe even let us use it to self-revive if we have it while we're on the ground, but make the health drain much faster because of it.
- Change the Medicine and Grenade slots into generic slots and let the player decide what to carry with them. For instance, let them carry two doses of meds if they don't have a bomb, or an extra bomb if they find a stash of them before they find more pills.
- While we're at it, give us new items to use in those slots. I can think of three right now: The Spray-n-pray, Body Armor, and Smoke Bombs. The Spray-n-Pray is a one time use flamethrower made of an aerosol can, a handle, and a lighting device. You can use it to quickly escape a Horde if you get surrounded or to do high damage against a Tank or something. It's range is short and narrow, so it doesn't tread too much on the Molotov's use. The Body armor lets you take less damage and makes you immune to friendly fire/explosions, but slows you down slightly, so you can choose between ether being safe from getting hurt occasionally or being able to evade getting hurt at all. Smoke Bombs act like being in a Smoker's Cloud, but with an advantage: Special Infected can't see your outline while your in them. Drop one in a hallway or a point you need to defend and you'll be safe (well... SAFER) from Special Infected attacks.
- Make the stationary machine-guns USEFUL. Right now there is no reason to ever use them on any level other than No Mercy's Finale... ether let us position them ourselves (by making us pick them up like gas cans) or put them in good locations and give them limited ammo to prevent them from becoming too powerful.
- More variety of weapons. What we have it great, but I'd love to see more... like a quick and powerful sawed-off shotgun, a fast shooting but inaccurate machine pistol, or a hunting revolver.
- Player Rankings for Online Play. I'm sick and tired of ether being stuck with people who don't know how to play or getting into a match with a pre-made of great players and getting curbstomped. Optional ranked match making would do a lot to help with that.