I'm definitely the kind of guy to do my best to save characters in games.
I don't know why, really, but I'm incredibly loyal to my squadmates in video games, AI or otherwise. When playing through stuff like Halo and Half-Life, I would always try to make sure that I keep any squadmates I come across alive until at least the end of the level. In the original Half-Life, this resulted in me having an entourage of (no joke) fifteen NPC's following me around, security guards and scientists all following me in a joint effort to stay alive.
In Left 4 Dead, I have risked my own life on numerous occasions to save other people. Most of the time, it doesn't end up in suicide, either. For instance: playing through No Mercy, we're on the finale map. I've got my auto-shotgun and I'm just wailing on everybody. The helicopter swoops in, just as we take down a tank, and I yell for everyone to book it. I'm the last one off the roof, and the others are running and gunning. One person gets jumped by a Hunter; I unload the rest of my ammo into the Hunter to shreds and hold off the horde with my pistols to let the other player up. We continue running. By now, one person is already on the heli, and the other is mid-jump.
All of a sudden, just as we're about to jump onto the heli ourselves (literally right next to it), the player who got jumped is swarmed and knocked down. Seeing this, I turn and run all the way back to the ammo pile, reload my shotty, come back and unload into the horde that has formed. I manage to save the person, get them back to their feet while the two in the heli cover us, and then hold off the horde as the player gets on the heli. All before jumping on myself and flying away.
Definitely the most proud moment I've ever experienced in multiplayer gaming, and it's a story that my friends tell all the time, now.
But yeah. Long story short, I try and save people, no matter the opposition. It's just how I roll.