Its weird that the more you play it the more you realise how dynamic it really is.. Its nowhere near as dynamic in single player as the ai is too predicable and not always great, but I've still sunk hours on solo.I purchased L4D1 for single player shooter. After one episode the game becomes incredibly monotonous and dull. I never finished it; and I typically finish all the games I start. It wasn't worth the money for me, and I paid $4.99 during the holiday last year.
I'd never call the l4d games dull.. Just goes to show how different peoples tastes are.