For me, the best part of UO was the ability to extend it, for me OSI was never pleasant to play on, but I was on an unofficial shard with Dragonlance saga backg

For me, the best part of UO was the ability to extend it, for me OSI was never pleasant to play on, but I was on an unofficial shard with Dragonlance saga background and it was the best time of my life, I don't think any other MMO could've been so extendible to fully implement that saga at those level of details