I am looking to getting into third-party-released DVDs. But before I do. I want to make sure if the Mill Creek DVDs has improved quality of the original DVDs releases. Do they have better quality than the original release or do they look worse compared to the original release?

From my experience, if this is a TV series, Mill Creek compresses the data to pack more episodes per disc. This in turn can reduce picture quality.

Are movies different from this?

They sometimes overcompress movies to fit several on one disc. If they want to appeal to those who prefer physical media over streaming, they need to stop that.

As long as they're using a studio-supplied master and not cramming 4 titles onto a single disk, I think their results are as good as anybody else's. Unless you're expecting two layers. The other downside is that they rarely/never carry over extras.

I was in a Wal-Mart maybe 2 years ago and was surprised to find new copies of "Go" (1999) and with a slipcover. At first I thought it was a warehouse find, but no. It was just Mill Creek's bare bones re-release. 6 months later I stumbled upon a used copy of the original at Dollar General.

Yes and no. Several of their 4-packs that were released a few years back had 2 discs with 2 movies on each disc, usually with Columbia/Tri-Star films.

If I remember, these discs were dual-layer and pretty good quality being 1 movie per layer. The original Columbia/Tri-Star versions of these titles had little or no extras anyways.

The nice thing about Mill Creek is that they always use anamorphic widescreen, no full screen crap.

Having said that, watch-out for their later releases which were 8 and 12-packs.
Some of these were heavily compressed with usually three and sometimes four 90 minute movies crammed onto a single dual-layer disc. They averaged about 3-3.5 mbps. DVD compression has come a long way but they start looking like youTube videos.

I've been generally pleased with the Columbia/Tri-Star MC releases. As orangerunner says they are anamorphic WS while the same Columbia disc will be FS (often sporting the original box art which says it's a WS/FS flippy - which I've successfully returned as defective when what's inside is the FS only disc). The only bad thing I'll say about them is they do not have SDH or CC. At least none I've purchased have this. I often watch late at night and use either so I can turn the volume down and not disturb my wife's sleep.

Almost all the Mill Creek Blu-rays I've bought have had SDH on them. It seems to have really started with that big batch of Sony double features they released around 2013. There have been others since then like Lady from Shanghai, Shakes the Clown and Spacehunter with SDH.

I'm still wary of them and confirm the presence of subtitles before I buy one of their releases. Kino and Olive have also gotten better about including subtitles over the last couple of years. The less said about Echo Bridge, the better.