I love a good old zombie game and at the moment i have become completely addicted to Left 4 Dead 2, But what other games are quite addictive with Zombies in? Preferably FPS.
You could try Resident Evil Survivor I and II though they were released for PSX and PS2 I am sure you can play the first one with any PSX emulator on your PC.
I suggest you to play an episode 'The Road to Ravenholm' in HalfLife 2. Awesome episode, a lot of zombies!
I don't think Resi 5 was that scary it had lost it's touch probable because there was someone with you