I checked the Greek site for Schengen Visa and this is the wording I found:-
Original documents (marriage certificates, birth certificates e.t.c) issued by other countries (other than the UK) need to have the apostille stamp or being ratified by the relevant Embassy.
Source:-
http://www.greekembassy.org.uk/Consu...izensOnly.aspx
Schengen Visa applications are full of twists and turns that can never be truly understood unless application is made. Yes, I know it's very frustrating but that's how they work. Each member country has their own slight (but important) differences.
The fact is that most supporting documents (not issued in UK) need to have the apostille stamp
or being ratified by the relevant Embassy.
Your marriage certificate
IS ratified (validated)
If you want to travel (say to Greece) then you will have to be compliant with the requirements. You only have what you have, and that actually does meet the stated requirement.
The only way to know 100% for sure is to make application.
I strongly suggest you also read the other requirements for supporting documents also.
Good Luck