[ScoobleDoodle]

If one isn't working in the games division of said company and one creates a game in their own free time, then no it is not unethical. Just because these mega corps have an interest in a broad spectrum of industries, that should not constrain employees working in unrelated sections from doing their own thing in their own time.

[mimixco]

Folks doing shift work don't usually have intellectual property constraints, but someone working on software for pay (even if it isn't games) who makes software and tries to sell it while he is working at company in that same business, regardless of the genre of the software title, is acting unethically.

Again, this is an argument in favor of working for yourself, which I totally support!