Looking at a few of my favorite games, I'm noticing a trend which wasn't common enough until just recently for me to actually see:
Half-Life 2
Bioshock Infinite
The Last of Us
A constant, likeable companion that you don't have to worry about in combat can really brighten a game right up. I've never had to load a game because I failed to protect Alyx, Elizabeth, or Ellie, which goes a long way toward not hating a character you're supposed to grow attached to. I was going to include Mass Effect and The Walking Dead in that list, but neither one really fits, since in ME your squaddies can die every time you take contact with no ill effect and TWD doesn't really have a combat system to worry about.
Half-Life 2
Bioshock Infinite
The Last of Us
A constant, likeable companion that you don't have to worry about in combat can really brighten a game right up. I've never had to load a game because I failed to protect Alyx, Elizabeth, or Ellie, which goes a long way toward not hating a character you're supposed to grow attached to. I was going to include Mass Effect and The Walking Dead in that list, but neither one really fits, since in ME your squaddies can die every time you take contact with no ill effect and TWD doesn't really have a combat system to worry about.