I would just give some names that are among my favorites :
Herbert, Silverberg, D i c k, Zelazny, Barjavel, Van Vogt, Vance.
Some french recent authors are more oriented to the way scifi was considered before (as in, with focus on concept and not really in 'TV serie' form) : Damasio, Bordage, Colin, Day. Some of them got the Hugo price if I remember correctly.
For fantasy, this is tougher since it's already itself a trash subgenre of fables, tales, legends, epic poetry. But outside of the author style (I read mostly french translations) there is Moorc o c k, a few of the preceeding cited authors (Zelazny, Vance, Day, Colin, Bordage, Barjavel), Homer, Chretien de Troyes, Lewis Caroll, Rabelais...
The last one being in an enlarge genre which keeps the same idea : comparing a contemporary society with a past one to illustrate some behaviors (or comparing gods and humans...)
I'm not a fan of Tolkien because I think he is indirectly responsible of the evolution of the genre into what it is today : moslty crap.
Edit : to pass censorshp.