99% of ICOs are designed for one purpose only - and that is to enrich the creator(s). In other words, yes, most of them are scams.

However, there are plenty of legit ICOs out there too. You just need to be very careful about which ones you choose to invest in. Do a lot of research in terms of the development team, whitepaper, road-map, etc. to gauge how successful you think it will be and then decide.