Mind you movies and TV shows that don't have THX still look great, but they're crystal clear. More like 89 to 90% clear, with some blur visible. Not a big problem -- I enjoy that quality, but THX-encoded DVDs are better. Reason being because they put more work to maintain the master of the master tape or film reel. DVDs without THX tend to make compressed copies of the original master (and I'm talking about the actual TV show/movie file, and the files containing the trailers; the rest of the work is done on computers; like multimedia etc.)
For this reason I believe that DVDs especially modern movies and TV shows tend to look blurry.
Remastered movies and shows are made specifically for DVD, so it tends not to look as blurry as the remastered product is the actual master itself, as opposed to a compressed file version of a modern TV show or movie.