The strategy makes it fun and immersive at times, but for the most part it gets old and repetitive quickly.
Left 4 dead 2 delivers some great graphics, but it's hardly any better than the original Left 4 dead; the only noticeable differences are better anti-aliasing, and higher resolution textures. If you like to watch the blood and guts fly, you're in for a treat with Left 4 Dead 2, where the gore factor is twice that of Left 4 Dead. Most of the Special Infected look slightly different in this game, but mechanically they are identical.
Let's talk about those new infected. They do add an interesting challenge to the game, and the three new special infected are three more threats to watch out for. The Spitter, Jockey and Charger are all new in L4D2, combined with the Hunter, Smoker and Boomer from the original game. The new Specials are similar in some respects to the returning ones, but they're different enough that you won't want to let your guard down. Also, witches walk around during daytime now.
The inclusion of a larger selection of weapons (More than five) is a welcome addition. New weapons include a total of four different shotguns, three assault rifles, a silenced SMG, a regular SMG, and two long-range rifles. Melee weapons are now available, and when carried take up the secondary weapon slot in place of your pistol. Unfortunately most of the new weapons aren't that much different from the ones in the first game to be considered unique. There are at least 8 different melee weapons, But they really all do the same thing, just with slightly different impact sound effects.
You've probably gathered by now that Left 4 Dead 2 is a lot like its predecessor, and you're right. There just isn't enough truly "new" content to warrant a new game. And unfortunately, Left 4 Dead 2 also suffers from the same shortcoming as the original game- mainly, it gets old quickly. You start in a safehouse, fight your way through hordes of zombies with the occasional special infected or Tank, the occasional gauntlet or crescendo event, in order to reach the next safe room. Eventually you reach the final crescendo event at the end of the campaign and escape, and move on to the next campaign to do the same thing all over again on a new map. It's fun at first, and teamwork makes it immersive for a little while, then the repetitiveness starts to take over. Now that I've beaten all the preloaded campaigns, I don't want to play them again, online or otherwise, because I know what I'll be doing and what's going to happen. Both L4D and L4D2 are pretty lacking in replay value.
In the offline single-player mode, the game's AI is still pretty lacking as well. More so than before the AI controlled players like to get in your way more than help you. They still regularly pick up and hand out pills and medkits they find, but have no clue what a pipe bomb is. They still tend to walk in front of you as you line up a shot. And now, they have even less of a clue what a pipe bomb is, gunning down Infected as they go for the bait, rendering the bomb useless as all its would-be victims are already dead by the time it goes off.
Left 4 dead does offer a couple new game modes. Realism mode is a new game mode which makes the game much harder, calling it a "real apocalypse". Realism mode removes the silhouettes normally seen on items and players through walls, and killed players in Realism do not respawn later in a chapter, instead having to wait until the next safe room. Mutation is a special challenge mode whose rules are changed and updated regularly by Valve. Realism Versus, a game mode originally released as one of these mutations, was so popular it was officially added to the game.
Left 4 Dead 2 is a generally good, entertaining game; however, it lacks any real replay value and doesn't add much new content with the exception of different maps, new guns and enemies. I feel like Valve has pulled a Call of Duty on this one. Nevertheless, you should check it out. If you played L4D and weren't too impressed, then obviously you should stay away.