Really simple games don't have to be bad. Canabalt for example is as simple as they come (your controls consist of a jump button) and the aesthetic is very simple by today's standards... but it's incredibly well executed in both gameplay and style.
Complex games typically become more and more enjoyable to me as I find new strategies and more nuances to old ones... to decline when I'm finding less and less new things and more and more flaws and limitations. Degenerate strategies, exploitable AI behaviour, interface limitations that don't let me automate things that have become routine... all of these result in less time spent on meaningful decisions and more time spent on going through the motions.
Games that offer extreme freedom and variety can remain deep and fun as an unequal challenge even after the realisation that they are utterly broken (venerable examples: MoO, MoM), but the Civ series never came close to that... they need to be robust enough to work as a semi-honest challenge. Civ5 isn't.
Complex games typically become more and more enjoyable to me as I find new strategies and more nuances to old ones... to decline when I'm finding less and less new things and more and more flaws and limitations. Degenerate strategies, exploitable AI behaviour, interface limitations that don't let me automate things that have become routine... all of these result in less time spent on meaningful decisions and more time spent on going through the motions.
Games that offer extreme freedom and variety can remain deep and fun as an unequal challenge even after the realisation that they are utterly broken (venerable examples: MoO, MoM), but the Civ series never came close to that... they need to be robust enough to work as a semi-honest challenge. Civ5 isn't.