I think Left 4 Dead 1 has a better overall cast of characters, however I think the improvements that Valve has made with Left 4 Dead 2 make it a much more fun and interesting experience. The addition of the new special infected, melee weapons and all of the new items really mix up the gameplay and keep you thinking on your feet whether your playing as a survivor or infected. Overall, while Left 4 Dead 1 is not a bad game by any stretch of the imagination, I feel like Left 4 Dead 2 is better because I feel like Valve took everything good and improved on it in Left 4 Dead 2.