1990-1995: The beginning
Trance was new and experimental. Not split up into sub-genres. Most of the best tunes were written during this time, but also a lot of stuff that wasn’t up to scratch.
1995-1998: The peak years
Sub-genres starting to appear, notably hard-trance, goa-trance, uplifting trance. Still loads of great tunes written during this time, and less crap. Most of what was called trance during this time was good, but trance was starting to get commercial, especially the uplifting trance.
1998-2001: The commercial years
Trance was everywhere, TV commercials, radio, lots of clubs. Time to cash in on the popularity.
Most of the best tunes during this time were in the sub-genres.
2001-2010: The end?
Trance isn’t trance any more. Mostly commercial and all sounds the same. Most of the good stuff is hard-trance.
If you look for it, a lot of what is called Psy-trance today still has the feel of the early trance (pre-1998), but there’s also a lot of boring, repetitive trash to sift through to find the gems.