MMO's are like dating, you always have a fondness for your first love.
Mine was Asheron's Call, and there's things about that game I just wish some of the more modernised titles would feature. Once a month there would be a regular free content patch that were churned out like a metronome. They would give teasers a couple weeks before it, and a couple weeks after people would be finding all the new things hidden about the world. As the storylines progressed the world changed to match. Many things were added to over time, extra features to improve the game and all for free; churned out like a metronome ticking away for years. Also the open skill system with no classes, you picked what you wanted and made your own classes. Looking forward to having that again in Champions Online (although its a different mechanic, and game entirely).