I thought Portal 2 was fantastic.
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I'd like to point out a crazy theory via just running around in the game and finding things online.
A) Chell is the daughter of someone at Aperture Science; her name is written behind the massive potato of the science projects from bring your daughter to work day.
A1) Chell might be Caroline's daughter. The turret opera, when translated, has numerous references of 'my girl' and 'my child.' A problem with this would be that Caroline is 'married to science' which implies she's probably single.
A1a) Good thing Chell is adopted.
Also, if this game doesn't win some sort of award for dialogue or voice acting, I'll be disappointed.