It's incredibly sad that by far the best MMO experience --- indeed one could say the only game which lived up to the promise of a shared, virtual, persistent world --- was also one of the first.

It was all downhill after WoW. It was a great game, but it was precisely because it was so good that it soon hegemonised everything. Rather than being one possibility out of many, it became "the" MMORPG, in that due to its success every subsequent game copied WoW, often superficially, and maybe even sometimes accidentally. Its specific conventions became the genre itself.