Sure,but how you gonna sell your tokens without ICO,no one will buy it when you directly listed it into exchanges.So you need to do ICO if you want to bring investors to your coins or your coins will become worthless without any demand.
You need directly in to the exchanges. But the only question is how do you introduce your tokens especially to thouse who intend to invest here if there is no ICO? Like others investors is to find a better platform for their investmen. May even be possible to introduce your tokens even in a small ways like airdrop to show your platform just for your tokens.