I will always prefer the first L4D over the second one. Why? No stupid melee weapons, no stupid extra special zombies and plus. It has lost a lot of seriousness that the first game had. People love Louis, Francis, Zoey and Bill. No one likes Rochelle (I also don't like Coach). If I were to play the second game, I would only play as Nick,
But to this game though, it means a lot to me. I feel heart broken when one of the 4 people die. I love them very much because they are so likeable. So when I kill one of them as an Infected, it shouldn't be the case but I get depressed. The environment in the episodes/maps is especially great. No fucking circus or Redneck swamp in sight because the first game is screaming ‘YOU ARE IN A SCARY, EERIE ENVIROMENT THAT IS REALLY DANGEROUS’ rather than ‘Oh look, you will fight clowns now or mudmen now.’
Get the first, buy the second if need be but the first one is the best.