I am not on "loose footing" at all. It has already been proven that being amazing at chess has nothing to do with intelligence. It has only to do with the amount of time spent playing. Intelligence only allows people to learn chess more quickly and grasp it more quickly than others. However, when you get to a certain point intelligence no longer plays a role and experience trumps all.
I'm arriving a little late to the party, but that isn't entirely correct. Intelligence accounts for a statistically significant portion of the variance in chess performance
after controlling for experience.
Here are some citations:
http://scholar.google.com/scholar?hl=en&q=Does+chess+need+intelligence%3F--A+study+with+young+chess+players.&btnG=&as_sdt=1%2C14&as_sdtp=
http://www.ulib.niu.edu:2222/science/article/pii/S0361923006000530?np=y
It is also known that intelligent people often choose faster thinking games. Obviously due to the fact that they can think faster than your average person. They don't need time to sit around and ponder things. They figure out what to do quickly because they are smart.
I had a quick look through the academic databases I have access using most combinations of the keywords Intelligence, Cognitive ability, Games, Genre, Choice and Preference and didn't find anything with those conclusions. That doesn't mean it doesn't exist, but I didn't find it. It's a really interesting conclusion and I'd really like to see the source.
I'm also fairly hesitant to equate fast performance in games with intelligence. Pattern recognition isn't the same thing as intelligence, and as you argue earlier, pattern recognition is likely heavily related to experience.
I guarantee that having to take faster turns in chess would result in the grand master slaughtering you even worse because the shorter turn time would have little effect on his decisions but you would be unable to figure out the optimal move in a short period of time. The same applies for Civ. The highly skilled players will perform well at a fast pace and lower skilled players will catch up to them at a slower pace due to having ample time to figure out the best move to make. While the skilled players know the best move to make quicker, they play practically on autopilot unless some really rare/novel/unique decision comes up.
I had a look at a study talking about blitz vs non-blitz chess and found a piece suggesting an interaction between skill and time on performance. Basically, at lower levels of skill limiting the time available actually equalized performance, but this effect lessened as skill got higher. So, at very high levels of skill, time played a less powerful role in predicting performance.
He also found that "..up to 81% of the performance variance in nonblitz chess was shared with blitz chess (Burns, 2007, p.446). The piece isn't addressing intelligence, but it is suggesting that "fast processes" such as recognition explain a large amount of the variability in chess ability both in blitz and non-blitz chess.
http://pss.sagepub.com/content/15/7/442.short
But, again, that doesn't allow conclusions about intelligence. Consistent with these findings, you could have low intelligence players who were good at pattern recognition excelling at both Civ5 (a "slow game) and SC2 ( a "fast" game).