This was such a great line. The first wave was decent, but all the same dragons was pretty lame. Wave 1.5 which was hard to find showed that good things were to come with that badass volcano and double headed dragon set.
The height of the line was Krystal Wars, multiple truly unique factions and dragons with a focus on dwarven esque cave dwellers and the boats/island port sets with wyvern esque dragons. Absolutely top tier stuff. Things got crazy ambitious with fire and ice, but personally I feel that it got a little too cartoony. Personal feelings aside, there was a lot of neat stuff on display, but sadly the plastic quality in these sets was much worse and many dragons and larger plate parts cracked/snapped/otherwise broke over time.
Plasma Dragons while kind of neat if you look at it in a vacuum was a huge step down at the time- everything from the figures to the dragons to the sets were smaller and less detailed. It did have a couple neat ideas and the figs did feature some ball joints, but overall it's nothing compared to the first few waves.
What else? The King Arthur sets are terrible, bland. The original designers had jumped ship for Lego by then. Dragons Universe is neat on paper- space Dragons! But the line never went anywhere or did anything exciting.
Pyrates was fantastic as well, while not as long lived it had all the strengths and none of the weakenesses of the Dragons line. It's essentially a perfect toyline.