Ok, 100K simultaneous online players is nothing to sniff at for any game. That's a success, that's a hit. Might not be a triple platinum mega hit but a hit nonetheless.
Absolutely. It's a huge achievement. However, in a discussion about the tastes of gamers and whether or not there's as much appetite for complex games today as there was when Civ was released, it says a lot that CoD is more than 100* as popular.
1. Free to play.
2. Marketing budget in the 9 figure range.
3. Comes from a long established series with ~20 games.
4. Available on all platforms.
I'd be willing to bet there's more of an appetite for complex games today than when Civilisation was released from an absolute standpoint, just that there's also more people playing games in general so from a relative standpoint there's less.
Pac-Man was probably also more popular than Civilization. Hardcore complex grand-strategy games are simply not as accessible to as many people as more mainstream games, but Paradox proves there's definitely a market for it.
COD sold 75-80 million copies [1]. Getting 30 million regularly implies that one of third of them are actively playing at the same time. That seems rather unlikely