What's the difference really? The movies I like, I would consider to be a cross between the two genres.

How would you classify movies like:

-The Poltergeist
-The Evil Dead 2
-White Noise
-The Ring
-Cemetery man
-The Shining
-Hide and Seek

???

Thrillers are meant to psyche you out (aka mindfuck).
Horrors are just full of gore.
Thus, thrillers are much better.

Evil Dead 2 was action/horror.
The Ring was just shitty.
The Shining was a thriller.
Hide and Seek was a thriller.

Thrillers are action flicks usually moving at a fast pace with a plotline that sometimes requires one suspend their disbelief. Thrillers are the film analog to a great Michael Crichton novel, such as Timeline, Jurassic Park, Congo, etc. - though some will certainly doubt the merit of the film versions of two of those three Crichton pieces.

Horror flicks are intended to terrify, often through the use of unsuspecting plot twists, supernatural elements, and, of course, gore. Such films can borrow the fast-paced plots and unbelievable elements of some thrillers.

IMHO, thrillers are devoid of supernatural elements, and are faster-paced than horror films which rely on suspense, and/or gore, and/or the supernatural.

I'd classify all of the films in your list as Horror (excluding Cemetery Man and Hide and Seek which I haven't seen).
Thrillers tend to be grounded in reality (although there are supernatural thrillers) and often crime (usually murder) related with an emphasis on suspense and mystery.
Although some are a little harder to classify: some of Argento's Giallo's with strong emphasis on violence e.g. Deep Red and Tenenbre - Hitchcock's Psycho - Silence Of The Lambs - maybe the Saw films at a push.
Just my two cents.