The team first of all. Without a solid team there's nothing. Secondly is the actually idea/project. If a great team is tackling something that nobody could make work, then it doesn't matter and I wouldn't be interested.
Simple and to the point, many people have begun to make some weird analysis in order to find the best ico when it is very easy to tell what projects have a chance to be a success and which projects dont and it all begins with the people that are creating the projects, if they are a bunch of people no one knows and the project seem unrealistic then the project is going to fail.
Often, I also like to see some form of prototype. This helps in the venture capital world, so why not here too.