I think it's inaccurate to look at IGG vs. Kickstarter as if it's a superficial distinction, as if it's Pepsi drinkers who are obviously going to buy Coke if that's all that's available. There are real differences that affect people's decision-making here.
Kickstarter has a very good and reliable reputation (important for something people perceive as inherently a little sketchy like crowdfunding.) It's a place many people already have an account (just the friction of signing up somewhere new and entering payment information is a big deterrent to many people.) It's a site a lot of well-heeled crowd-funders already visit regularly, which dramatically improves discoverability, and which is sending out emails to all those people who already signed up. (Its userbase is apparently around 3 million people, which is nothing to sneeze at.) It has an external ecosystem of stuff that IGG doesn't (the obvious thing that comes to mind is Kicktraq.) Kickstarter has exactly one funding model, and no customer confusion about it.
Maybe most significantly, Kickstarter pledges are collected at the end, which means anyone can cancel a pledge no-harm-no-foul earlier during the campaign -- IGG locks you in and makes you talk to a CS rep to get a refund if you really want to cancel. Even though the vast majority of people don't cancel their pledges, the ability to do so helps ease people in to pledging money to this type of campaign -- when it's not easy to reverse a pledge, people are going to be more reticent to pledge in the first place. All of this stuff goes into people's thought processes when they make a call on buying into a campaign like this.