If you “unsubscribe” to unsolicited emails, all it does is verify that your email address is valid and ‘live,’ therefore worth more to them when they sell your details on spam lists. Don’t do that.
Once you’re on their lists, the only real option you’ve got for a permanent solution is to change addresses. Choose a name that’s hard to guess; a lot of spam is sent to speculative addresses, so if your email is something like “chris@webmail.com” or “info@yourdomain.com” you’re going to get spammed to death.
Most of my email goes through one or another of the well-known webmail providers these days. I get very little unfiltered spam.