Leucius: At the risk of offending atheists in the crowd, it made me think on my philosophy on life and whether or not I wanted to continue on the path of being an asshole and troll (I used to start flamewars for fun) or if I wanted to become a better person. This all happened several years after I initially played the game, though. It left a lasting impression on me. I had to decide if I wanted to be a "good guy" or just out for self.
These days I try to be nice to everyone, and I try to show respect, even if people don't always respect me. It's a challenge, but I'd like to think there's something beyond this life, and I'd like to think the good deeds I do have a ripple effect and make the world (or at least my community) slightly less shitty.
dtgreene: As an atheist myself, I can say that being a better person does not require any sort of religion. Being a bad person doesn't require it either, though there is a strong correlation there, however.
The way I see it, religion is commonly used to justify horrible acts.
In any case, I do try to respect people, provided those people show me a reasonable amount of respect.
Incidentally, one game that left a lasting impression on me was the NES version of Ultima 4.
Sorry, I didn't clarify in that post that what I meant by my philosophical meanderings was whether or not to believe in a higher power. Hence, I didn't want to offend atheists. I just forgot to put that part in there :)