To sue an ICO, you must talk to a lawyer in the jurisdiction of the founders, and see about the viability. Laws differ in all jurisdiction on the subject matter and may just be a waste of time. Any reputable lawyer will give you at least a 30 minute talk for free - I would have - to just give you an assessment of the viability of the action you seek.
If it's in US, then, I dare to say that it's viable, but it has to do with how the ICO document was written, risk factors, your due diligence and so on. So before you go to a lawyer, gather up all the documents, and arrange them so it will be easy to understand for a legal professional.
Now, here comes my general advice: never invest in an ICO that have no product up. Anyone that want to launch an ICO - also take heed: first you seek angel capital, don't raise from the public. First create a viable alpha or at least beta product, and preferably get in a number of users BEFORE you raise money from the public. The inverse is true: if you don't know the guys behind the ICO, then don't invest until there is a viable product and you can verify that the guys can actually do the job at hand. If you raise funds, remember: that you expose yourself to risk. Same if you invest into something.
Best way to reduce risk, is to stage the products in multiple roll-outs, and the raise can increase; as an investor, the smaller the raise is the overall risk reduces as an exit scam is less likely.
As for myself, im a software engineer, served as CTO, software architect, lead programmer and so forth for about 30 years. I also have a degree in law, which i don't really use, other than for private or corporate litigation, so I never take on external clients for legal work. So I'm giving this advice in a general manner for both parties.