Depends on what it is you're watching dude.
An example of something that looks pretty bad is Highlander.
A good HD remaster is Ben-Hur (remastered and restored frame by frame from the 65mm film negative).
TNG HD remasters look grainy for a lot of footage (like on the bridge), but there's still quite a bit of stuff that looks better than the DVD versions. They used the best source in all cases.