A very good question, with no simple answer, other than no, often they are not.
This varies due to many factors, but remastered records are often worse than early pressings, and very occasionally better.
Here’s what we know about analog recordings made on tape (as almost all analog recordings are): they offer the highest resolution, but deteriorate over time. The very best versions of the masters, mix-down masters, sub-masters and various analogs that make their way to the record pressing facilities are the ones made as close to when the original analog recordings were made.
What this means for records is that the early ones or those closest to the recording are often the best, all other things being equal. Better still, you want an early pressing from one of the first stampers made from the first mother – the moulds used to create the moulds used to press records. That’s because the moulds deteriorate every time they are used and the original master recording deteriorate from the moment they are made and every time they are played.
Add to this the fact that record plants, equipment, technicians and the people that operate the tape machines were all at their peak years ago, not right now, and the tendency for remasters to be produced too hot and you have a combination that renders modern remasters often disappointing. Don’t just take my word for it though, you can read more about this in many great articles online, like this good primer for example.
That being said, if you get the right album, remastered by the right engineer, in the right studio, with really good, intact analog masters as closely as possible to the originals, with good quality, clean vinyl that’s been well pressed, thick and flat, remasters can sometimes sound better than the originals, or at least as good. The problem is, there are not enough like this!