I'm a bit tempted to get into LCGs as well. I've been leaning towards WI, but thats because I (and my group) are a bit more familiar with Warhammer than the others, and I've seen more explanation of WI than the other 2.
Which one is the most widely popular out of the three at the moment? Do any of them show any signs of stopping?
More importantly, I'd like to know if any of them are clearly going to be around for the duration. Cthulhu is the game I most want to play, but since I'm late coming into it, I don't want the game to end right when I've put a good deck together. Games have had a habit of doing that to me.
"Truth has power. And if we all gravitate toward similar ideas, maybe we do so because those ideas are true…written deep within us. And when we hear the truth, even if we don't understand it, we feel that truth resonate within us…vibrating with our unconscious wisdom. Perhaps the truth is not learned by us, but rather, the truth is re-called…re-membered…re-cognized…as that which is already inside us." Peter Solomon, The Lost Symbol
Using the un-scientific forum activity as an indicator of the size of each game I'd say Cthulhu lags behind the other 2.
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Not to mention Warhammer invasion is substantially newer, so considering the amount of posts and topics, it is a lot more active then the other 2.