Here we are roughly one year after the release of Left 4 Dead, and its sequel is already out. For Valve, Left 4 Dead 2 represents an unusually speedy turnaround time considering the delays and release date fuzziness generally associated with its games, notably in the years leading up to Team Fortress 2 and the still mysterious status of Half-Life 2: Episode 3. Despite that history and the potential concerns associated with how soon this game is showing up after the first, Left 4 Dead 2 is very much a complete game, much more so than the original, and is without a doubt the better product. If you're still in the mood to group up with friends and slay packs of ravenous undead, then it doesn't get any better than this. However, if you're tired of Left 4 Dead's gameplay formula, the sequel, as good as it is, may not be enough to warrant a purchase. It's a game that's more about refinement and augmentation of existing features instead of offering something dramatically new.
As a result, after you've played Left 4 Dead 2, it's difficult to go back to the original without a mild sense of disappointment. Remember, of Left 4 Dead's four original campaigns, only two were set up for Versus play right out of the gate. It wasn't until Valve released the Survival Pack months later that players got the full Versus experience as well as the now-standard timed Survival mode. Left 4 Dead 2 has five full and more interesting campaigns, a more fleshed out and distinctive setting with some fantastic action set pieces, more personality, more modes, and in general gives you more to do. In many ways, I wish this would have been the product that was released first since it feels much more full-featured than the original, and the fiercely team-oriented style of gameplay wouldn't have been as familiar then as it is now.