Lord of Light - 302 pages. I recall this being a fairly long novel when I read it. Every novel out of Wizards of the Coast is now 310 pages.
Nine Princes in Amer - 172 page
Courts of Chaos - 142 pages
Fareinheit 451 - 208 pages
Riddle Master of Hed - 228 pages
Dragonflight - 320 pages
Elric of Melnibone - 192 page
So, it is not ENTIRELY true that fantasy and SF used to be shorter, but in general, so many well know SFF books from the 60's and 70's were much shorter than they are today.